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Class U _ L2 7> , 


Book ■ M 6_ 

I 7 M 

CojpghtN°__ 


COPYRIGHT DEPOSIT. 


















Electrical Equipment 

of the 

Motor Car 


A One Volume Edition Combining 
those Portions of “Electrical Equip¬ 
ment of the Motor Car” and 
“ Automotive Electrical Systems ” 
as have been Found Most Help¬ 
ful to the Automotive Electrical 
Student and to the Repairman 


By David Penn Moreton 

\ s 


New York 

U. P. C. BOOK COMPANY, Inc. 
239 West 39th Street 
1924 




TL 

• .M6 


Copyright. 1918, 1920, 1923, 1924 
By U. P. C. BOOK COMPANY, Inc. 


£c j~/n^. 


PRINTED IN THE U. S. A. 

BY FREDERICK GUMBRECHT, BROOKLYN, N. Y. 


JAN 10 

©C1A76C703 


Electrical apparatus play such an important part in the 
design and operation of the modern motor car that it is prac¬ 
tically impossible to intelligently operate or repair any motor 
vehicle without some knowledge of the fundamental principles 
of electricity and their practical applications to the motor car. 

The electrical equipment of the motor car has been re¬ 
garded as being something quite mysterious and impossible for 
anyone only an expert to understand. This impression has in a 
great measure been due to a lack of authentic information on 
the subject which would .meet the immediate requirements of 
the reader. The majority of books which treat of the applica¬ 
tions of electricity as applied to the motor car assume the 
readers are fairly well acquainted with the fundamentals of 
electricity and, as a result, the minds of the readers are often 
very much befogged by trying to follow a rather technical 
description of some kind without having had the fundamental 
principles thoroughly explained. There are a great many in¬ 
dividuals who feel that they have a fairly good knowledge of 
the fundamental .principles of electricity yet they are unable 
to apply these principles in working out their problems in con¬ 
nection with the repair and maintenance of the electrical equip¬ 
ment of the motor car. The numerous electrical terms and 
phrases are very frequently improperly used by the men about 
service stations which is an indication that the individuals using 
them are not thoroughly acquainted with the true meaning of 
the terms and phrases and their proper application. 

In the preparation of the manuscript for this book, the 
authors have endeavored in the first few chapters to present the 
fundamental facts and relations in connection with the electrical 
and magnetic circuits in a clear logical manner, in order that 
the readers may easily follow the practical applications of these 
? acts and relations as found in the actual equipment on the 
motor car which is thoroughly described in the remaining chap¬ 
ters of the book. An effort has been made to compare the 


IV 


PREFACE 

action of the electrical and magnetic circuits to the more com¬ 
mon things of every day life with which the readers are familiar 
and for this reason such analogies as the analogy of the flow of 
electricity to the flow of water, and similar comparisons have 
been freely used throughout the book. The operation of the 
electrical equipment itself is treated on the basis of the funda¬ 
mental principles involved in its operation rather than describ¬ 
ing each particular make of equipment by itself, thus enabling 
the readers to analyze the operation of the equipment which is 
a great deal more satisfactory than memorizing a set of writ¬ 
ten instructions. 

In brief, the subject matter is presented with the idea in 
mind of trying to get the readers to think electrically and thus 
reason out their own problems rather than use the common cut- 
and-try methods so frequently employed. 

Numerous special wiring diagrams are given throughout 
the book which have been specially prepared so as to illustrate 
the actual electrical equipment and its installation in a clear 
and simple manner. 


DAVID PENN MORETON. 


CONTENTS 


CHAPTER I. 

Fundamentals of Electrical Circuit. 9 

Electrical Circuit. Ampere. Electrical Current. Elec¬ 
tricity Moving Force. Electrical and Water Circuits. 
Pressure the Essential Factor. Resistance to the Flow 
of Electricity. Relation of Current, Pressure and Resis¬ 
tance. Conductors and Insulators. Factors Determining 
the Resistance of a Conductor. 

CHAPTER II. 


The Series Circuit.. .27 

Resistance of Series Circuit. Pressure and Current 
Relations in a Series Circuit. Examples Illustrating Cur¬ 
rent Relations in a Series Circuit. Examples Illustrating 
Current Relations. Pressure in Series. Arrangement of 
the Parts of a Series Circuit. Internal Resistance. Cal¬ 
culating Resistance for Battery Charging, 

CHAPTER III. 


Parallel Circuits .43 

Resistance of Parallel Circuits. Conductance. Pressure 
and Current Relations for the Parallel Circuit. Examples 
Illustrating Relations of Parallel Circuits. Combined Series 
and Parallel Circuits. Pressures in Parallel. 

CHAPTER IV. 

Making Electricity Do Work.58 

Force. Work. Energy. Comparison of Water and 
Electrical Circuits. High and Low-Pressure Circuits. Con¬ 
servation of Energy. 






VI 


CONTENTS 
CHAPTER V. 


Electrical Power .. .70 

Measurement of Electrical Power. Relation Between 
Mechanical and Electrical Power. Measurement of Elec¬ 
trical Energy. How to Determine the Cost of Charg¬ 
ing Storage Batteries. Torque. Determining Torque 
Starting-Motor Must Develop. 


CHAPTER VI. 

Primary Catteries .82 

Voltage Cell. Primary and Secondary Cells. Action 
of a Primary Cell. Polarization. Depolarization. Local Ac¬ 
tion. Electrochemical Equivalent. Damage Due to Elec¬ 
trolysis. Polarity Indicator. The Leclanche Cell. Dry 
Cell. An Electric Battery. Proper Combination of Cells 
for Best Results. 


CHAPTER VII. 


Storage Batteries .95 

Distinction Between Primary and Storage Batteries. 
Types of Storage Cells. Lead Storage Cells. Chemical 
Action Within a Storage Cell When Discharging. Chem¬ 
ical Action When Charging. Arrangement of Plates in 
a Lead Storage Cell. Containers for Lead Storage Cells. 
Electrolyte for Lead Storage Batteries. Ampere-Hour and 
Watt-Hour Capacity of a Storage Cell. 


CHAPTER VIII. 

Care of Storage Batteries.110 

Charging the Battery. Care of Battery When Not in 
Service. 


CHAPTER IX. 

Magnets and Magnetism. 117 

Artificial Magnet. Poles of a Magnet. North and 
South Poles. Magnetic Attraction and Repulsion. In¬ 
duced Magnetism. Forms of Magnets. Demagnetization. 
Coercive Force. Retentiveness. Molecular Theory of 
Magnetism. Magnetic Pole of Unit Strength. Magnetic 
Field. Lines of Force. Magnetic Screen. 







CONTENTS vii 

CHAPTER X. 

Electromagnetism. 129 


Direction of Magnetic Field. Determining the Direc¬ 
tion of Magnetic Field. Solenoids. Polarity of Solenoid. 
Magnetomotive Force. Reluctance. Permeability. Ohm’s 
Law for the Magnetic Circuit. Reluctance in Series and 
Parallel. Hysteresis. 


CHAPTER XI. 

Electromagnetic Induction .141 

Currents Induced in a Wire by a Magnet. Current 
Induced in a Coil by Moving a Magnet. Value of the In¬ 
duced Pressure. Direction of Induced Pressure. Deter¬ 
mining the Direction of Pressure. Primary and Secondary 
Coils. Mutual Induction. Unit of Inductance. 

CHAPTER XII. 


Generators and Motors.154 

Simple Alternator. Simple Direct-Current Generator. 
Four-Segment Commutator. Simple Ring Armature. Mul¬ 
tipolar Ring Armature. Simple Drum Armature. Elec¬ 
trical Pressure Induced in Armature Winding. 

CHAPTER XIII 

Fields and Windings for Generators and Motors.168 

Types of Magnetic Fields. Parts of the Magnetic Cir¬ 
cuit. Series Generator. Shunt Generator. Compound 
Generator. 

CHAPTER XIV. 

Generator Output and Purpose of Cutout.177 

Operation of Self-Excited Shunt Generator. Constant- 
Current and Constant-Voltage Output. Purpose of the Cut¬ 
out. Two-Pole Cutout. Arrangement of Windings on 
Cutout. Location of Cutouts. Manual Cutouts. 

CHAPTER XV. 

Regulation of Generator Output...191 

Cumulative Action of Series and Shunt Field Windings. 
Differential Action of Series and Shunt Field Windings. 








Vlll 


CONTENTS 


Bucking Series Field Winding. Third-Brush Machine, 
Electromagnetic Regulation. Mechanical Regulation. 
Regulation by Ampere-Hour Meter. Suggestions in Ad¬ 
justment of Regulators. 

CHAPTER XVI. 

Electric Motors...223 

Principle of the Direct-Current Motor. The Left-Hand, 
or Motor, Rule. Generator and Motor Interchangeable. 
Operation of Two-Part Commutator. Multiple Coil Arma¬ 
tures. Types of Magnetic Fields. Magnetic Leakage. 
Excitation of Direct-Current Motors. Armature Reaction 
in a Motor. Proper Position of the Brushes on a Direct- 
Current Motor. Demagnetizing and Cross-Magnetizing 
Ampere Turns. Commutation. Reducing Armature Reac¬ 
tion. Counter Electromotive Force. Torque Produced by a 
Motor. Speed of a Motor. Output of a Motor. Opera¬ 
tion of a Shunt Motor. Operation of the Series Motor. 
Compound Motor. Starting Motors. Motor Generator, 
Dynamotor. The Dynamotor as a Starting and Lighting 
Unit. 

CHAPTER XVII. 


Motor and Engine Connection.266 

General Requirements of Starting Motor. Overrunning 
Jaw Clutch. Overrunning Roller Clutch. Overrunning 
Ratchet-and-Pawl Clutch. Friction Clutch. Non-Auto¬ 


matic Pinion Shift. Automatic Electromagnetic Pinion 
Shift. Bendix Drive, or Automatic Pinion Shift. Old 
Bosch-Rushmore Electromagnetic Drive. Direct Applica¬ 
tion of Starting Motor. Back-Kick Releases. Location of 
Starting Motors. Purpose of Generator Drive. Friction 
Drive for Generator. Belt Drive for Generator. Chain 
Drive for Charging Generator. Gear Drive for Charging 
Generator. Mounted Directly on Engine Shaft. Com¬ 
bined Generator and Motor Drives. Gear Housings. Gear 
Reductions. Starting, Lighting and Ignition. Relation 
Between Functions. Difference in Names. Three-Unit 
Systems. Two-Unit Systems. Single-Unit System. Gen¬ 
eral Classification of Systems. Operating Voltage. Single 
and Multiple-Voltage Systems. 

CHAPTER XVIII. 

Switches and Protective Devices.319 

Single and Multiple Switches. Kinds of Switches. Con¬ 
trol and Location of Switches. Fuses and Circuit Breaker. 





CONTENTS 


IX 


CHAPTER XIX. 


Electric Lamps . 333 

Lamp Filaments. Classification of Lamps by Base. Care 
of Lamp Reflectors. Lamp Reflectors. Focusing Lamps. 
Wiring and Light Switches. Dimming Headlights. 


CHAPTER XX. 


Electrical Instruments .345 

Most Widely Used. Ammeter Shunts. Principle of the 
Voltmeter. Combined Ammeters and Voltmeters. Ampere- 
Hour Meter. Wattmeter. Watthour Meter. 


CHAPTER XXI. 


Ignition Systems.360 

Early Methods of Ignition. Low-Tension Ignition Sys¬ 
tem. High-Tension Ignition System. Fundamental Prin¬ 
ciples of Jump-Spark Coil. Purpose of Condenser in 
Jump-Spark Coil. 


CHAPTER XXII. 


The Magneto .371 

Fundamental Principle of Magneto. Simple Form of 
Magneto. Dixie Magneto. Berkshire Magneto. Simms 
Magneto. Mea magneto. Low-Tension Magneto. High- 
Tension Magneto. Safety Gap. Friction-Drive Magneto. 

Gear and Chain-Drive Magnetos. Impulse Starters. 


Sumpter Impulse Starter. Spark Timing. 

CHAPTER XXIII. 

Battery Generator Ignition.398 

Open and Closed Circuit. Current Lag. Time Con¬ 
stant. Atwater-Kent System. Bosch System. Con¬ 


necticut System. Pittsfield System. Remy System. 
Rhoades System. Westinghouse. Philbrin. Delco Sys¬ 
tem. The Resistance-Unit Function. Delco Interrupter. 
Delco Ignition Relay. Single-Ignition System. Dual 
and Double Ignition. Two-Spark Ignition. 







X 


CONTENTS 


CHAPTER XXIV. 


Spark Plugs .441 

Arrangements of Electrodes. Series Spark Plug. Mag¬ 
netic Type of Plug. Waterproof Plugs. Priming Plugs. 
Airplane Type. Plug Threads. Gap Between Electrodes. 


CHAPTER XXV. 

Ignition Wiring and Timing.451 

Timing Battery System. 


CHAPTER XXVI. 

Electric Signals and Accessories.455 

Electrical Alarms. Care of Electric Horns. Spot 
Lights. Trouble Lamps. Electric Heaters. Signals and 
Direction Indicators. The Electric Brake. Electric 
Vulcanizers. 


CHAPTER XXVII. 

Electric Gearshifts and Transmissions.466 

Wiring of Gearshift. Woods Dual Power Car. Mag¬ 
netic Braking. Entz Transmission. General Arrange¬ 
ment of Parts. Various Positions of Controller. Elec¬ 
tric Braking. Merits of Entz Transmission. 


CHAPTER XXVIII. 

Reading Wiring Diagrams . 485 

General Discussion. Wiring Diagrams and Symbols. 

A Typical Installation. Tracing the Circuit. Using 
a Wiring Diagram. Analysis of Trouble. 


CHAPTER XXIX. 

Maintenance and Repair of Electrical Equipment and How 
to Diagnose Electrical Troubles . 

Part I.—Points on Maintenance and Repair. Solder¬ 
ing Joints in Wiring. Care of Generators and Start- 








CONTENTS xi 

ing Motors. Regulating Generator Output. Care of 
Storage Battery. 

Part II-—Testing Equipment. Ammeter and Volt¬ 
meter. Partial List of Testing Equipment. 

Part III.—Classification of Troubles, Simple Tests. 

Part IV.—Testing Out Complete Circuits. 

CHAPTER XXX. 

Stock Ford Ignition and Lighting System.524 

General Discussion. Magneto Terminal Connections. 
Ignition System. Lighting Circuit. Horn Circuit. 
Combination Switch and Dimmers. Ignition Trouble. 

Oil Troubles. 


CHAPTER XXXI. 

F-A Starting and Lighting Systems on the Ford Car 


537 




















































































































































































. 








ELECTRICAL EQUIPMENT 
OF THE MOTOR CAR 

CHAPTER I 

Fundamentals of Electrical Circuits 

E LECTRICITY in its many applications, as found on the modern 
motor car, plays no small part in the successful and satisfactory 
operation of the motor car as a unit and the degree of comfort and 
luxury it is possible for the manufacturer to provide. 

It is responsible for the spark that ignites the mixture of gas 
and air in the cylinder and makes the engine operate; it lights the 
car, starts the engine, and operates the horn. There are cars in 
which it heats the fuel; others in which it shifts the gears and in 
some still newer designs, even replaces clutch and gearset in the 
transmission of the power of the engine to the rear wheels. 

The exact nature of electricity is not known and no attempt will 
be made to give any explanation as to what it may be. You can, 
for convenience, think of electricity as being the name given to that 
something which produces certain results which we call electrical, 
such as lightning, the arc formed when a trolley wheel breaks con¬ 
tact with the trolley wire, the sparks formed in stroking the cat’s 
back, etc. We are all familiar w T ith the fact that if we step out 
of a window without any means of support, we are sure to fall to 
the ground or sidewalk. The reason of our falling is due to the 
attraction of the earth on our bodies, which is called gravity. The 
exact nature of this attraction is not known any more than the exact 
nature of electricity is known. The action of gravity under cer¬ 
tain definite conditions, however, is well known, and so is the action 
pf electricity under certain definite conditions quite well known. 


10 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


Since we know the action of electricity under definite conditions, 
it is possible to make practical use of it in operating the lamps, 
starting, motor, etc., on the motor car, even though its exact nature 
is not known. For the sake of convenience in dealing with elec¬ 
tricity, we can think of it as a fluid such as water, but it must be 
remembered at all times that this similarity has to do with the 
action only and does not necessarily mean that the two are identical. 


The Electrical Circuit 

The electrical circuit is the fundamental basis of the many appli¬ 
cations of electricity to the motor car, and, in order to understand 



Figs. 1 and 2 —Electrical and water circuits contrasted. The electrical 
circuit at the left must be complete before there will be a current of 
electricity, but the water system, at right, need not be a complete circuit 
for a current of water to flow in it 

thoroughly the principles, operation and maintenance of these appli¬ 
cations, it is essential that we have a quite complete knowledge of 
the electrical circuit and its more common properties and char¬ 
acteristics. 

The electrical circuit is the path in which the electricity flows, 
just as the water pipe is the path in which the water flows or a 
river bed is the path in which a river flows. 

There is one great difference, however, between the electrical cir¬ 
cuit and the ordinary circuit in which the water flows, and that is 















FUNDAMENTALS OF ELECTRICAL CIRCUiio 11 

that the electrical circuit is always closed on itself while the water 
circuit is not necessarily always closed. 

This difference may be illustrated by two different examples as 
follows: Suppose we take a small lamp and connect it to a storage 
battery by means of wires and a switch, as shown in Fig. 1. There 
will be no flow of electricity through the lamp unless the switch is 
closed, or, as we say in practice, unless the circuit is complete. In 
the case of the flow of water in a pipe, the pipe may be conducting 
the water from one tank to another as shown in Fig. 2 and it is not 
necessary to have a pipe from the second or lower tank back to the 
first or higher tank in order that there be a flow of water in the 
pipe. 

The fact that the electrical circuit must he complete and cannot 
merely conduct electricity from one point to the other , as the pipe 
conducts water from one tanlc to the other, Fig. 2, is the keynote of 
the electrical circuit. Referring to Fig. 1—the complete electrical 
circuit is made up of many parts, wires, lamps, switch, battery ter¬ 
minals, battery plates, electrolyte, etc., all combined in a continuous 
path, circle or circuit, as you choose to call it. 

We can think of the electrical circuit just as we think of the 
circle; that is, it is continuous and has neither beginning nor end. 
If we start at any point on the electrical circuit and follow along 
the circuit we will arrive at the point from which we started just 
as we return to the starting point in following along a circle, regard¬ 
less of the point from which we started. 

In order to emphasize the importance of the reader getting this 
circuit or circle idea thoroughly in mind, the various circuits of the 
modern motor car are indicated in their circular form in Fig. 3. 
These circuits and their relations to each other will be taken up in 
detail later. It is not humanly possible to make changes or locate 
troubles in the electrical equipment of a car unless this circuit idea 
is followed, either consciously or unconsciously. 

The circle or circuit is to electricity what the metal rails are to 
the railroad train. Your train cannot run without the track, as 
electricity cannot be made use of except in a circuit. 

Let us draw a circuit parallel from nature: If we follow a drop 
of water along one of Nature’s circuits, as shown in Fig. 4, the 
water falls as rain upon the ground, runs into the little brooks, 
creeks, larger rivers and then into the ocean, where it is in turn 
evaporated by the . sun, then carried over the land in the form of 


12 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



SECONDARY CIRCUIT 


IGNITION SWITCH 


MOTOR 


PRIMARY CIRCUIT 


STARTING <5W)TC1 


IGNITION 


STARTING 


CUTOUT 


J6HTJNG 

SWITCH 


‘HARGING 


LIGHTING 


LAMPS 


SIGNALLING 


HORN BUTTON 


Fig. 3 —The major circuits in the motor car. Starting, lighting, igni¬ 
tion, signalling and all electrical features of the car are operated in 
complete circuits which are indicated here as circles 















FUNDAMENTALS OF ELECTRICAL CIRCUITS 



13 


Fig. 4— Nature’s great water circuit, typical of the electric circuit. A drop of water falls as rain 
upon the ground, runs finally into a river and thence into the ocean, where it is evaporated by the sun and 
carried back in the form of clouds over the land and again falls as rain to repeat its travels again and again 







14 ELECTRICAL equipment of the motor car 

clouds by the wind, and again falls as rain. The path of the water 
in this great natural circuit—which we will call Nature’s circuit— 
corresponds in a great measure to the electrical circuit inasmuch as 
it is a circle, a system without start or finish, beginning or end. 

It is evident that in Nature’s water circuit there may be an ac¬ 
cumulation or decrease in the quantity of water at any point in the 
circuit. That is, the amount of water evaporated by the sun in a 
given time is not necessarily equal to the quantity falling as rain 
in the same time. Nor is the amount flowing into the ocean from 



Figs. 5 and 6 —Simple water and electrical circuits. The battery may 
be likened to the pump and the wire to the water pipe. Both of these 
circuits are complete 


the rivers in a given time necessarily equal to the amount running 
into the rivers from their various tributaries and along their banks 
in the same time. 

In an electrical circuit similar to Fig. 1, the quantity of electricity 
leaving the lamp is exactly equal to the quantity of electricity en¬ 
tering the lamp and the same quantity of electricity returns to 
the battery as leaves it. There is no accumulation of electricity at 
any point along the electrical circuit similar to the accumulation of 
water at different points along Nature’s water circuit. 

The operation of a water circuit similar to the one shown in Fig. 5 
corresponds more nearly to the operation of the simple electrical 
circuit than Nature’s water circuit. The water circuit illustrated 
in Fig. 5 consists of a pump P connected to a curved piece of pipe. 














FUNDAMENTALS OF ELECTRICAL CIRCUITS 
When the pipe and pump are filled with water the flow of the water 
in the pipe, due to the action of the pump, will be very similar to the 
flow of the electricity in the simple electrical circuit shown in Fig. 6, 
whch consists of a piece of wire connected to the terminal of a stor¬ 
age battery. Both of these circuits are complete; they are closed 
on themselves and, like the circumference of a circle, have neither 
beginning nor end. 

The quantity of water entering one end of the pipe from the pump 
is exactly equal to the quantity of water leaving the other end of 
the pipe and entering the pump. Likewise the quantity of elec¬ 
tricity entering one end of the wire from the battery is exactly 
equal to the quantity of electricity leaving the other end of the 
wire and entering the battery. The pump does not produce the water 
but merely causes the water to flow through the pipe. The battery 
does not create electricity, but merely causes the electricity to flow 
through the wire. 

Electrical Current 

It is obvious that the action of the pump in the water circuit 
and the action of the battery in the electrical circuit are very 
similar. There is a mechanical pressure produced by the pump which 
causes the water to flow through the pipe, and the battery produces 
what is called an electrical pressure which causes the electricity to 
flow through the wire. 

If the mechanical pressure produced by the pump be increased or 
decreased, there will be a change in the flow of the water in the 
pipe, the flow increasing with an increase in pressure and decreasing 
with a decrease in pressure. This flow, or movement of the water 
in the pipe, may be measured by determining the number of gal¬ 
lons passing a certain point in the pipe in, say, 1 second. You 
could then speak of the flow of water in the pipe as being so many 
gallons per second. Any unit of quantity and time may be used in 
expressing the flow of water in a pipe, such as so many cubic feet 
per minute, so many gallons per hour, etc. 

The flow or movement of electricity in the electrical circuit is 
measured in a similar manner to the flow of water in a pipe; that is, 
by determining the quantity of electricity passing a certain point in 
the electrical circuit in a certain time. Instead of measuring the 
quantity of electricity in gallons or cubic feet, as in the measurement 
of water, it is measured in a unit called the coulomb. 


16 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


In referring to a certain quantity of electricity it is spoken of as 
so many coulombs just as a certain quantity of water is spoken of 
as so many gallons, so many cubic feet, etc. 

The Ampere 

If the water in a pipe, such as the one shown in Fig. 5, is moving 
at such a rate that there is 1 gallon of water passing every point 
along the pipe each second, there is said to be a flow of 1 gallon 
per second in the pipe. Similarly, if the electricity in a circuit, 
such as the one in Fig. 6, is moving at such a rate that there is 1 
coulomb passing every point in the circuit in each second of time, 
there is said to be a flow of 1 coulomb per seeond. The flow, or 
movement of the water in the pipe, is called the current of water, 
just as the flow of the water in a river is called the current, and, 
likewise, the flow of the electricity in the electrical circuit is called 
the current of electricity or more commonly the electrical current. 
Thus it is seen that the current of water is expressed as so many 
gallons per second, so many cubic feet per minute, etc., while the cur¬ 
rent of electricity is expressed as so many coulombs per second. 

Fortunately we have a special name for this rate of flow of elec¬ 
tricity of one coulomb per second, which is called the ampere. This 
way of giving the rate of flow a special name relieves us of the 
necessity of saying “per second’’ each time, as w r ould be the case if 
we were to speak of the current as so many coulombs per second. 
Thus a current or rate of flow of 10 coulombs per second is just 10 
amperes; 50 coulombs per second is 50 amperes, etc. We are not 
interested in the quantity of electricity alone, but in the rate of flow, 
the ampere, and for this reason the coulomb is very little used. 

Unfortunately there is no name for the rate of flow of water, and 
we always have to use some such cumbersome expression as gallons 
per second, cubic feet per minute, etc. 

The Volt 

The number of gallons per second of water flowing through a 
pipe depends in a large measure upon the pressure causing it to flow. 
This pressure in the water circuit is measured as so many pounds 
per square inch or so many pounds per square foot. In a similar 
manner, the current of electricity, in amperes, in a wire depends 
in part upon the pressure under which the electricity flows. 

The electrical pressure is mersured in a unit called the volt. The 


FUNDAMENTALS OF ELECTRICAL CIRCUITS 


17 


volt means exactly the same thing in speaking of an electrical cir¬ 
cuit as the pound pressure does in speaking of the water circuit. 
A higher pressure will be required to force the same current of water 
through a small than through a large pipe, and a higher electrical 
pressure will be required to force the same current of electricity 
through a small wire than through a large one. Similarly higher 
pressures will be required in both the water and electrical circuits 
if the length of the circuits be increased; that is, if the length of 
the pipe and wire be increased. 

Electricity Moving Force 

The pressure produced by the pump might be called the water 
moving force, while the pressure produced by the battery may be 
called the electricity moving force or electromotive force. The elec¬ 
tromotive force is usually represented by the abbreviation e.m.f. 

If pressure gauges be connected at various points along the water 
pipe, Fig. 7, they will indicate the pressure at the different points. 
There will be a difference in the pressure as indicated by the various 
gauges, if there is a current in the pipe, and their indications will 
be less and less as you pass along the pipe in the direction in which 
the water is flowing. The difference in the value of the pressure as 
indicated by any two of the gauges connected to the pipe will rep¬ 
resent the pressure acting on the portion of the pipe between the two 
points where the gauges are attached. This difference in pressure 
between two points on a pipe is called the drop in pressure or merely 
the drop between the two points. The pressure between two points 
along a stream of water is often spoken of as the difference in level, 
the drop in level or merely the drop between two points. 

In the case of the electrical circuit, there is a difference in the 
electrical pressure between two different points along the circuit. 
This difference in pressure between any two points is measured in 
volts just as the total pressure produced by the battery is measured 
in volts. The pressure at any point in an electrical circuit cannot 
be measured by attaching a suitable instrument to the circuit at that 
point alone, similar to the attachment of the pressure gauge to the 
water pipe, but the instrument must be attached to two points as 
shown in Fig. 8, and then it does not read the pressure at any par¬ 
ticular point but the difference in the pressure between the two 
points on the circuit where it is connected. This difference in pres¬ 
sure, or voltage, as it is usually called, between any two points along 


16 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

a circuit is sometimes spoken of as the drop between the two points. 

The water in the pipe flows from a point of higher pressure toward 
a point of lower pressure. The electricity in the electrical circuit 
flows from the point of higher electrical pressure or higher electrical 
level toward the point of lower electrical pressure or electrical 
level. In the electrical circuit the point of higher pressure is usually 
marked with the plus sign ( + ) and the one of lower pressure with 





Figs 7 and 8 —The pressure in an electrical circuit, at the right, changes 
along the wire just as the pressure in the water circuit, at the left, 
decreases along the pipe—How the difference in pressure is measured 

the minus sign (—). The terminal of the battery from which the 
electricity flows when the battery is discharging, is called the posi¬ 
tive terminal, while the terminal toward which the electricity flows 
is called the negative terminal. 

Any point along the wire will be positive with respect to points 
further along the wire in the direction of the current, and negative 
with respect to points along the wire opposite the direction of the 
current, just as the pressure indicated by any gauge is higher than 
the pressure indicated by gauges connected to the pipe at points 
further along the pipe in the direction of the water current and 
lower than the pressure indicated by gauges connected to points 
on the pipe opposite the direction of the water current. 


















FUNDAMENTALS OF ELECTRICAL CIRCUITS 


19 


To explain: In Fig. 8 point A is at a higher electrical pressure 
than B, likewise B is at a higher electrical pressure than C, so that 
B is positive with relation to C, but negative with relation to A. 

The reader should have clearly in mind by this time the distinc¬ 
tion between amperes and volts. The amperes represent the value 
of the current in the circuit—that is, the number of coulombs of 
electricity that pass through the circuit during one second, while 
the volts represent the pressure causing this current or movement 
of electricity. 

Resistance to the Flow of Electricity 

It is possible in both the water and electrical circuit to have a 
pressure acting in the circuit when there is no current. It is per¬ 
fectly plain that if the path of the water be blocked or interrupted 
by closing a valve in the pipe, Fig. 9, there will be no current of 



Figs 9 and 10 —The effect of resistance. In a water circuit, if the valve 
is closed, there icill be no flow of water, though there may be a high 
pressure at the pump; in the electrical circuit if the wire is cut or 
switch is opened there is no current, though the battery may have a 
high electrical pressure 

water, although there may be a high pressure produced by the 
pump. If the path in which the electricity moves is blocked or in¬ 
terrupted by opening a switch or cutting the wire, there will be 
no current in the circuit, although the pressure may be high. 












20 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The currents of water and electricity are, therefore, dependent 
upon something besides the pressure. This something which opposes 
the flow of water in the water circuit and the electricity in the 
electrical circuit is called the resistance of the circuit. The resis¬ 
tance of an electrical circuit simply opposes the free flow of ele- 
tricity through the circuit; yet the resistance does in no way tend to 
cause the electricity to flow in the direction opposite to that in 
which it is flowing. If you push against the wall of a building, 
the wall opposes the action of your force, yet the ivall will not push 
you backwards w-hen you stop shoving. 

The greater the resistance of an electrical circuit the less the cur¬ 
rent a certain pressure will produce and the smaller the resistance 
of the circuit the greater the current a certain pressure will produce. 

There is no unit in which the resistance offered by a pipe may be 
measured. The resistance of an electrical circuit is measured in a 
unit called the ohm. A circuit is said to have a resistance of 1 ohm 
where an electrical pressure of 1 volt will produce a current in the 
circuit of 1 ampere. 

Electrical and Water Circuits 

The following table gives in condensed form the names of the 
units in which the common qualities associated with the electrical 
and water circuits are measured: 



Water 

Electricity 

Quantity 

Gallon, cubic foot, etc. 

Coulomb 

Current 

One gallon per minute, one cu¬ 
bic foot per minute, etc. 

Ampere 

One coulomb per second 

Pressure 

Pounds per square inch or 
pounds per square foot 

Volt 

Resistance 

No unit 

Ohm 


Pressure the Essential Factor 

When a current of water is to be produced in a pipe, the one 
thing above all others which must be present in the circuit is the 
pressure. The pressure in the circuit shown in Fig. 9 is produced 
by means of the pump. The circuit may be blocked by means of a 


FUNDAMENTALS OF ELECTRICAL CIRCUITS 21 

valve and there will be no current regardless of the value of the 
pressure. If the valve be opened or the circuit completed, there will 
be no flow of water in the circuit unless there is a pressure acting 
in the circuit. 

The same general conditions exist in the case of the electrical 
circuit. If the wire forming the circuit be broken, or if the cir¬ 
cuit is opened at a switch, as shown in Fig. 10, there will be no cur¬ 
rent in the circuit regardless of the value of the pressure. If the 
circuit be completed, there will be no current unless there is an 
electrical pressure acting in the circuit. It is thus seen that it is 
imperative that there must be a pressure acting in every closed 
circuit in order that there be a current in the circuit. 

The electrical pressure for practical purposes on the motor car 
may be produced by chemical action as in the primary and storage 
battery, or by electromagnetic induction as in the generator. Both 
of these methods will be discussed in detail in two of the following 
sections. 

Relation of Current, Pressure and Resistance 

The current in an electrical circuit increases with an increase 
in pressure, provided the resistance of the circuit does not increase 
in value faster than the pressure. If the resistance of the circuit 
remains constant, the current in the circuit will increase and decrease 
directly as the pressure; that is, if the pressure acting in the circuit 
be doubled, the current in the circuit will be increased to twice the 
original value, and if the pressure be decreased in value, say, to one- 
half its original value, the current will decrease in value to one- 
half its original value. 

The current in an electrical circuit decreases with an increase 
in resistance, provided the pressure in the circuit does not increase 
in value faster than the resistance. If the pressure in the circuit 
remains constant, the current in the circuit will vary in value in¬ 
versely as the resistance of the circuit; that is, if the resistance of 
the circuit be doubled, the current in the circuit will decrease to 
one-half of its original value, and if the resistance be decreased 
in value, say, to one-fourth of its original value, the current will 
increase in value to four times its original value. 

The above relations between current, pressure and resistance 

are stated as follows: 

Current varies as pressure divided by resistance. When the cur- 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


rent in the circuit is measured in amperes, the pressure in volts 
and the resistance in ohms, this relation between current, pressure 
and resistance may be stated as follows: 

current = pressure -f- resistance, or 

pressure 

current = -— 

resistance 

amperes = volts -§- ohms, or 
volts 

amperes — - 

ohms 

A storage battery is connected to a lamp as indicated in Fig. 1. 
The pressure produced by the battery is 6 volts and the resistance 
of the lamp is 12 ohms, what current will the battery produce in 
the lamp? By referring to the above relation between current, 
pressure and resistance, we see that the current is equal to the pres¬ 
sure in volts divided by the resistance in ohms, and if we replace 
“ pressure’* by the value of the pressure in volts and “ resist¬ 
ance” by the value of the resistance in ohms, we may determine 
the value of the current in amperes as follows: 

pressure 6 

current =-, or current = — = V 2 ampere 

resistance 12 

If the current in a circuit and the pressure producing the cur¬ 
rent are both known, then the resistance of the circuit may be de¬ 
termined as follows: Since the current is equal to the pressure 
divided by the resistance, we may write the resistance equal to pres¬ 
sure divided by the current as follows: 

resistance = pressure -f- current, or 

pressure 

resistance =-- 

current 


ohms = volts -r- amperes, or 
volts 

ohms =- 

amperes 

For example, if the pressure acting in a light circuit of a motor 
car is 12 volts and there is a current of 4 amperes, then the resis¬ 
tance of the circuit is equal to 12 divided by 4, or 

12 

resistance == — = 3 ohms 

4 






FUNDAMENTALS OF ELECTRICAL CIRCUITS 


23 


In some eases the resistance of the circuit and the current it is 
desired to produce are known and the problem is to find the pres¬ 
sure necessary to produce this desired current. The pressure in a 
circuit in volts is equal to the resistance of the circuit in ohms mul¬ 
tiplied by the current in amperes, or 

pressure = resistance X current 
volts = ohms X amperes 

For example, if the resistance of a lamp is 3 ohms, what pressure 
will be required to produce a current of 2 amperes through the 
lamp? We may determine the value of the pressure required in 
volts by replacing the resistance in the last equation by the value 
of the resistance, the current by the value of the current and then 
multiplying these two quantities, thus 

Pressure = 3 X 2 = 6 volts 

Conductors and Insulators 

Some materials will offer less resistance or opposition to the flow 
of electricity through them than other materials, and for this rea¬ 
son they are called conductors, while those materials which offer 
a high opposition to the flow of electricity through them are called 
insulators. For example, copper, iron, brass, carbon, lead, etc., offer 
a comparatively low resistance to the flow of electricity through 
them, and hence they are called conductors. 

Rubber, glass, fiber, mica, porcelain, etc., all offer a high oppo¬ 
sition to the flow of electricity through them, and hence they are 
called insulators. You must get this fact clearly in mind that all 
materials will conduct electricity, but the conducting power of some 
is much better than others, and they are called conductors merely 
to distinguish them from the materials which are poor conductors 
of electricity and called insulators. The words conductor and insu¬ 
lator are only relative terms and the readers must not get the 
impression that some materials will conduct electricity and some will 
not. In practice, the conducting power of the ordinary insulating 
materials, such as rubber, porcelain, mica, etc., is so-poor in com¬ 
parison to the conducting power of the conductors, such as copper, 
brass, iron, carbon, etc., that they are said to conduct no electricity. 

Factors Determining the Resistance of a Conductor 

The resistance offered by a pipe to the flow of water through it 
depends upon the size and length of the pipe. The greater the 
length of the pipe, the greater the resistance it will offer to the 


24 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

flow of water through it, and the shorter the pipe the less the 
resistance it will offer to the flow of water through it. 

The resistance offered by a wire to the flow of electricity through 
it depends upon the length of the wire just as the resistance of the 
pipe depends upon the length of the pipe. The longer the wire, the 
greater the resistance, and the shorter the wire, the less the resis¬ 
tance, the size of the wire, of course, remaining constant. If the 
length of the wire be increased to twice its original value, its resis¬ 
tance will be doubled, while if its length be reduced, say to one- 
third its original length, the resistance will be reduced to one-third 
its original value. In other words, there is a direct relation between 
the resistance of a wire and its length. 

If the area of a pipe be increased; that is, if the pipe be replaced 
by a smaller one of the same length, there will be an increase in 
the resistance to the flow of water, while if the area of the pipe 
be increased there will be a decrease in the resistance. There is a 
similar relation between the resistance of a wire and its area or 
size. If a wire of a certain length be replaced by a smaller wire 
of the same length and of the same kind of material as the first, 
there will be an increase in the resistance, while if the size of the 
wire be increased, there will be a decrease in the resistance. 

A pump which is producing a certain pressure will cause more 
water to flow through a short pipe than through a large one of 
the same size, it also will cause more water to flow through a large 
pipe than through a small pipe of the same length. Likewise, a 
battery which produces a certain electrical pressure will cause a 
greater flow of electricity in a short wire than in a long wire of the 
same size and of the same material; it also will cause a greater flow 
of electricity in a large wire than in a small wire of the same length 
and of the same material. 

The relation between the resistance of two wires of the same 
size and composed of the same material will be exactly the same 
as the relation between their lengths. That is, if one of the wires 
is ten times as long as the other one, then its resistance will be ten 
times as great as the other wire. If two wires are of the same 
length and composed of the same material but of different size, 
the relation between their resistances will be just the opposite to 
the relation between their areas. That is, if one wire has an area 
three times as large as the other one, its resistance will be one- 
third as great as that of the other wire. 


FUNDAMENTALS OF ELECTRICAL CIRCUITS 


25 


The resistance of a wire depends upon the kind of material of 
which the wire is composed. Thus copper is a better conductor of 
electricity than aluminum; aluminum is better than brass; brass 
is better than iron; iron is better than lead, etc. A copper wire 
of a certain size and length will have less resistance than a brass 
wire of the same size and length; the brass wire will have less 
resistance than an iron wire of the same size and length, etc. 

Since the resistance of a wire increases with an increase in length 
and decreases with an increase in area, we have the following 
relation: 

The resistance of a wire varies as the length divided by the area. 
This relation, stated in a little different form, means that the re¬ 
sistance increases at the same rate that the length increases, if the 
area remains constant, and the resistance decreases at the same 
rate that the area increases. If the length and area of a wire both 
increase at the same rate, the resistance of the wire will remain 
unchanged. 

The resistance of a wire is not constant, even though its length 
and area remain constant, but changes, due to a change in tem¬ 
perature. The change in resistance of some materials due to a 
change in their temperature is very small, and in some cases may 
be neglected. Some materials experience an increase in resistance 
with an increase in temperature, while there is a decrease in resis¬ 
tance with an increase in temperature in some. Carbon, for ex¬ 
ample, decreases in resistance with an increase in temperature, 
while the resistance of brass, iron, copper, etc., increases with an 
increase in temperature. The increase in resistance of a copper wire 
is approximately 2 %oo 1 P er cent f° r each degree increase in 
temperature on the Fahrenheit thermometer. Thus, if a coil of cop¬ 
per wire has a resistance of 100 ohms at 60 degrees, its resistance 
at 100 degrees may be determined approximately as follows: 

Multiply the change in temperature by .0022 and the result by 
the original resistance, if the temperature is increasing, and the 
result will be the increase in resistance, thus: 

300 — 60 = 40 degrees change in temperature 
40 X .0022 XI00 = 8.8 ohms increase 
100 -f- 8.8 = 108.8 resistance at 100 degrees 

In brief, the resistance of a conductor depends upon three things, 
and they are: 


26 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

(a) Dimensions of the conductor (its length and area). 

(b) The kind of material in the conductor (whether it is copper, 

brass, iron, etc.). 

(c) The temperature of the conductor. 


i 


\ 




CHAPTER II 

The Series Circuit 

T F a water circuit be composed of two pipes and they are connected 
A in the manner indicated at A and B in Fig. 11, they are said to 
be connected in series. There is only one path through which the 
water may flow in passing from the outlet of the pump and return 
to the pump. The current of water at any instant is the same at 
every point along the two pipes, and just exactly as much water is 
returning to the pump in a given time as is leaving the pump. The 
water is not used up in the operation of such a circuit. The circuit 



Figs. 11 and 12 —A series electrical circuit and a series water 
circuit compared 

is complete and, as in the case of the circle, has neither beginning 
nor end. 

Note that the water is not used up in this operation, but some of 
its ability to do work is used. 

An electrical circuit composed of two or more different wires of 
perhaps different sizes, lengths and materials, and connected as 
shown in Fig. 12 is called a series circuit. In this case, there is only 
one path through which the electricity may flow in passing from the 
positive terminal of the battery and return to the negative terminal 

















28 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of the battery. The current of electricity is the same at every point 
along the different wires, and just exactly as much electricity is 
returning to the battery in a given time "as is leaving the battery in 
the same time. 

The electricity is t not used up in the operation of such a circuit, 
but its ability to do work is used, just as in the case of the water. 
This will be explained more in detail later. 

A series water circuit is found in the operation of the cooling sys¬ 
tem of some early motor car engines, as shown in Fig. 13. In this 
case, the four waterjackets of the different cylinders, the radiator, 
the pump and the connecting pipes are all in series. The current of 
water through the different parts of the circuit at any time is exactly 
the same; just as much water returns to the pump as the pump sends 



Fig. 13 —A series xcater circuit as employed on some early cars. 
The pump, pipes, water jackets and radiator are in series, for the 
water has only one path in which to flow 


into the circuit. This method of cooling is not a good one, but is 
used here for the purpose of bearing out the series circuit idea. 

When the headlights on motor cars are connected as shown in Fig. 
14, they form a typical series electrical circuit. The current of 
electricity through the different parts of the circuit at any time is 
exactly the same; just as much electricity returns to the battery as 
the battery sends into the circuit. The electricity is not consumed 
in the lamps, hut some of its ability to light lamps is used. 

Resistance of Series Circuit 

Since the resistance offered by a pipe to the free flow of water 
through it increases with an increase in the length of the pipe, it is 






















THE SERIES CIRCUIT 


29 


evident that the resistance of two pipes connected in series will be 
greater than the resistance of either pipe alone. If the two pipes 
are of exactly the same size and length, they will, when connected in 
series, offer twice the resistance to the flow of water through them 
that is offered by a single pipe. If the pipes are of the same size 
but of different lengths, they will offer a combined resistance equal 
to that of a single pipe of the same size but having a length equal 
to that of the combined lengths of the two pipes. 

Two wires of the same size and material will, when connected in 
series, offer a combined resistance equal to that of a single wire of 
the same size, but having a length equal to the combined lengths of 
the two wires. 

Any number of electrical resistances, such as motor car lamps, 



Fig. 14 —A series electric lighting circuit. The battery, sivitch 
wires and lamps are in series, for the current has only one path 
in which to flow 


connected in series might be thought of as being equivalent to a num¬ 
ber of wires of the same size and material but having different 
lengths, and the combined resistance of any number of resistances 
in series is equal to the sum of the different resistances. For ex¬ 
ample, if the two lamps in Fig. 14 each have a resistance of 2 ohms, 
the combination will have a total resistance of 4 ohms. In order to 
get the total resistance of the circuit, the resistance of the leads, 
switch, etc., should be added to the resistance of the lamps. 

Pressure Relations for a Series Circuit 

If pressure gauges be connected along a water pipe, as indicated 
in Fig. 15, in which there is a current of water, the difference in the 

















30 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

readings of the different gauges will bear the same relation to each 
other as exists between the distances between the points to which 
the gauges are connected. For example, the difference in the reading 
of gauges G1 and G2 will bear the same relation to the difference in 
the readings of gauges G2 and G3, as the distance between G1 and 



Fig. 15 —The difference in pressure along a tvater circuit is pro¬ 
portional to the length of the pipe 


G2 bears to the distance between G2 and G3. If the distance be¬ 
tween G2 and G3, which we will represent by L2 is twice the distance 
between G1 and G2, which we will represent by LI, then the differ¬ 
ence in readings of G2 and G3 will be twice the difference in the 
readings of G1 and G2. 

The reason for this relation may be explained as follows: Since 
the resistance between the points where G2 and G3 are connected will 
be as many times the resistance between the points where G1 and G2 
are connected as the length L2 is times the length LI, the pressure 
between the points where G2 and G3 are connected must be as many 
times the pressure between the points G1 and G2 are connected as 
L2 is times LI, in order to produce the current in the pipe. The 
differences in pressure between different points along a series water 
circuit will bear the same relation to each other as exists between the 
resistances between the points where the pressures were measured. 

In the electrical circuit, the voltmeter measures the difference in 
pressure between the points along the circuit to which the terminals 
of the voltmeter are connected. Thus in Fig. 16 there are two volt¬ 
meters connected so as to measure the difference in pressure between 
two different sets of points. If the wire composing the circuit is of 
the same material and same size all the way along the circuit, then 
the reading of the two voltmeters VI and V2 will bear the same 
relation to each other as exists betwen the lengths LI and L2. If the 
length L2 is twice the length LI, then the resistance R2 is twice the 
resistance Rl, and since the value of the current in R2 is exactly the 
















THE SERIES CIRCUIT 


31 

same as the value of the current in R1—neglecting the current 
through the voltmeters—there will be twice as much pressure re¬ 
quired to produce this current in R2 as is required to produce it in 
Rl, which will result in the reading of Y2 being twice the reading 
of Yl. When the resistance R2 is three times the resistance Rl, then 
the reading of Y2 will be three times the reading of Yl etc. 

The electrical pressure acting on a part of the resistance of a series 
circuit, bears the same relation to the pressure acting on some other 
part of the same circuit as exists between the resistances of the two 
parts. That is, if two resistances are connected in series and they 
have exactly the same resistance, then the pressure acting on each 
of them will be exactly the same when there is a current of the 
same value through them. If, however, two resistances are con¬ 
nected in series and the resistance of one is twice that of the other, 
then the pressure acting on the one of lower resistance will be one- 
half of the pressure acting on the one of higher resistance. 

If two lamps having different resistances be connected in series, 
the pressure acting on one lamp will not be the same as the pressure 
acting on the other lamp. The lamp of higher resistance will have 
a higher pressure acting on it than the one of lower resistance. This 
relation accounts for the fact that two lamps of different candle- 
power and the same voltage will not operate satisfactorily in series, 
because the one of lower candlepower, or higher resistance, will have 
a larger part of the total pressure acting on it than the one of high 
candlepower, or lower resistance. Thus you cannot put a 6-volt, 24- 



Fig. 16— The difference in pressure along an electrical circuit is 
proportional to the length of the wire 

candlepower, headlight in series with a 6-volt, 2-candlepower dash- 
light, and operate them from a 12-volt battery, but you can put two 
6-volt, 24-candlepower headlights in series with a 12-volt battery, or 
one 6-volt 2-candlepower dashlight and one 6-volt 2-candlepower 
taillight in series with a 12-volt battery. 



















32 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

A 6-volt lamp may be operated on a 12-volt battery by connecting 
a resistance in series with the 6-volt lamp as shown in Fig. 17. The 
resistance in series with the lamp must be equal to the resistance of 
the lamp, in order that the pressure over the lamp be 6 volts or one- 
half of the total pressure. The pressure over the lamp may be de¬ 
creased by connecting more resistance in series, or increased by de- 



Fig. 17— Using a 6-volt lamp with a 12-volt battery by putting 
a resistance in series 

creasing the amount of resistance in series. This principle is used 
by some companies in dimming the headlights, as the decrease in 
pressure on the lamp decreases its candlepower. 

Current Relations in a Series Circuit 

The reader must always have in mind that the current in every 
part of a series circuit is exactly the same and that there is no ac¬ 
cumulation of electricity at any point along the circuit. An ammeter 
connected at any point in a series circuit will indicate the same cur¬ 
rent as long as there is no change in the value of the resistance of 
the circuit or the total pressure acting in the circuit. 

If a series"circuit be opened at any point by means of a switch, if 
a lamp burns out or a wire breaks, there will be no current in the 
circuit and an ammeter connected in the circuit will indicate zero cur¬ 
rent regardless of where the ammeter may be connected. 

The current in a circuit, in amperes, is usually represented by the 
capital letter I, the pressure in volts by the capital letter E, and 
the resistance in ohms by the capital letter R. 
























THE SERIES CIRCUIT 


33 


Examples Illustrating Current Relations 

A certain 6-volt headlight takes a current of 4 amperes when it is 
connected to a pressure of 6 volts. What resistance must be placed 
in series with the lamp in order to operate it from a 12-volt battery? 
Since the pressure necessary to operate the lamp is one-half of the 
total pressure in this case, then the resistance required in series with 
the lamp will be equal to the resistance of the lamp. The resistance 
of the lamp, which we will represent by RL, will be. equal to the 
pressure required to operate it divided by the current the lamp 
takes, or 

6 

RL = - = 1 y 2 ohms 
4 

Therefore the resistance that must be placed in the circuit is 1% 
•hms. 

If this same 6-volt lamp is to be operated on a 24-volt battery, the 
procedure in determining the value of the resistance to be placed in 
circuit is a little different. The resistance and the lamp will carry 
the same current, since they are in series. The pressure over the 
resistance which we will represent by ER will be equal to the total 
pressure, E, of the battery, minus the pressure over the lamp EL or 

ER = E — EL 
ER = 24 — 6 
ER = 18 volts 

The value of the resistance then is equal to the pressure acting on 
the resistance divided by the current through the resistance, or 
R = 18 divided by 4 = 4% ohms 

The resistance of the lamp, if it takes a current of two amperes, 
is equal to 

6 divided by 4 = iy 2 ohms 

It is interesting to note that in each of the above cases, the rela¬ 
tion between the resistance of the lamp and the resistance to be con¬ 
nected in series with it is the same as the relation between the pres¬ 
sure acting on the lamp and the pressure acting on the resistance in 
series with the lamp. 

Since the lamp requires a pressure of 6 volts, the pressure acting 
on the resistance to be placed in series will be the difference between 
the total pressure, or 24 volts, and the pressure acting on the lamp, 
or 6 volts, which gives 18 volts. The resistance that must be placed 
in series with the lamp will t>e equal to as many times the lamp re- 


34 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

sistance as the pressure which is to act on the series resistance is 
times the pressure acting on the lamp. The pressure acting on the 
series resistance in this case is three times that acting on the lamp, 
hence, the value of the series resistance must be three times the value 
of the resistance of the lamp. The resistance of the lamp is equal 
to the pressure on it divided by the current through it, or 6 divided 
by 4, or 1%, ohms. Hence, the value of the series resistance will 
be equal to 3 times 1*4 or 4% ohms. 

Pressures in Series 

If two pumps be connected as shown in Fig. 18, the pressure pro¬ 
duced by one pump will act with the pressure produced by the other 
pump and the combined pressures of the two pumps will act upon the 
water circuit to which the combination is connected. Several pumps 
may be connected in this manner and the sum of the pressures pro- 



Fig. 18 —Boosting the pressure in a water circuit by putting 
pumps in series 


duced by the combination, when they are producing a pressure in the 
same direction around the circuit, will be equal to the total pressure 
acting in the circuit. Thus, if each of the pumps indicated in Fig. 
18 is producing a pressure of 50 pounds, the total pressure acting in 
the circuit to which the pumps are connected will be equal to the 
sum of two pressures or 100 pounds. 

If the pressures produced by the pumps are unequal, the total 
pressure is equal to the sum of the pressures, just the same. For 
example, if the pumps are producing pressures of 75 and 25 pounds 
per square inch, respectively, the total pressure acting on the circuit 
t,o which they are connected will be equal to 75 plus 25 or 100 pounds 



















THE SERIEo CIRCUIT 


35 


per square inch. If two men shove against a car in the same direc¬ 
tion with a force of 100 and 125 pounds, the total force acting on the 
car is equal to the sum of the two forces or 225 pounds. 

Several electrical pressures may be connected in a similar man¬ 
ner to the pumps, as indicated in Fig. 19, which represents two dry 
cells in series. If the pressure produced by each of the dry cells 
acts in the same direction, then the total pressure will be equal to 
the sum of the pressures of the two cells, regardless of whether the 
pressures produced by the cells are equal or unequal in value. Thus, 
if the pressures produced by the two dry cells are 1.2 and 1.4 volts, 
respectively, the total pressure will be equal to 1.2 plus 1.4 or 2.6 
volts. 

If a number of equal pressures be connected in series so they all 
act in the same direction around the circuit, then the total pres¬ 
sure will be equal to the product of the number of pressures con- 



Fig. 19 —Boosting the pressure in an 
electrical circuit by connecting dry cells 
in series 


neeted together and the value of one of the pressures. For example, 
if six dry cells, each producing a pressure of 1.5 volts, be connected 
series, then the total pressure will be equal to six times 1.5 or 9 volts. 
If ten men are all pushing on a car in the same direction and each 
is pushing with the same force, say 100 pounds, then the total force 
acting on the car will be equal to ten times the force of a single 
man, or 1,000 pounds. 

In order that the pressures produced by the pumps act in the same 
direction around a water circuit, it is necessary to connect the sides 
of the pumps of lower pressure to the sides of higher pressure in 
regular order. If pressure gauges be connected to the circuit as in¬ 
dicated in Fig. 18, it is possible to determine the pressure produced 











* 86 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

by either of the pumps or any combination by observing the indica¬ 
tions of the proper gauges. 

For example, the pressure produced by the pump PI is equal to 
the difference in the pressure before and beyond the pump, which 
may be determined by reading the gauges G1 and G2 and then sub¬ 
tracting the lower reading from the higher reading. The pressure 
produced by the pump P2 may, in a similar manner, be determined 
by taking the difference in the readings of the gauges G2 and G3. 
The pressure produced by each pump tends to cause the water to 
flow through the pump itself from the terminal of lower pressure 
toward the terminal of higher pressure, and through the water circuit 
to which the pump is connected from the terminal of higher pressure 
toward the one of lower pressure. All of the pumps will be acting 
in the same direction when the pressure gauges on, say the right- 
hand side of the different pumps, all read higher than the pressure 
gauges on the left-hand side, or all of the gauges on the left-hand 
side read higher than all of the gauges on the right-hand side. 

If some of the pumps are connected in the circuit so that the 
pressure they produce is opposed to the pressure produced by the 
other pumps, then the pressure acting in the circuit will be equal 
to the difference between the sum of the pressures acting in one 
direction and the sum of the pressures acting in the other direction. 
If the sum of the pressures acting in one direction is exactly equal 
to the sum of the pressures acting in the opposite direction, then 
the pressure acting in the circuit tending to produce a flow of water 
will be equal to zero. 

The direction of the pressure acting in the circuit when there are 
pressures in both directions, will correspond to the larger sum. For 
example, if six pumps are connected in such a manner that the pres¬ 
sure produced by two of them is in the opposite direction to the 
pressure produced by the remaining four, it is obvious that the pres¬ 
sure acting in the circuit to which the pumps may be connected is 
not equal to the sum of the pressures produced by all six pumps, 
but it is equal to the difference in the sum of the pressures produced 
by the four pumps and the sum of the pressures produced by the 
two pumps. 

If each of the six pumps is producing a pressure of 10 pounds, the 
pressure acting in the circuit may be determined as follows: The 
pressure produced by the four pumps will be equal to the pressure 
produced by a single pump multiplied by four, or 10 X 4, or 40 


THE SERIES CIRCUIT 37 

pounds. The pressure produced by the two pumps likewise is equal 
to 10 X 2, or 20 pounds. 

The pressure acting in the circuit is equal to the pressure in one 
direction subtracted from the pressure in the opposite direction, or 
40 — 20 = 20 pounds. The direction of this pressure of 20 pounds 
will be the same as the direction of the larger sum of 40 pounds. The 
same results could be accomplished by using two pumps alone instead 
of six, as the pressure of two of the six pumps which are acting 
in one direction is exactly neutralized by the pressure of two of the 
six pumps acting in the opposite direction. 

It is obvious that if ten men are pushing on a car—say, six in a 
certain direction and four in an exactly opposite direction—that the 
force tending to move the car is not equal to the combined forces 
produced by the ten men but it is equal to the force produced by the 
six men minus the force produced by the four men or 600 — 400 = 
200 pounds. The direction of this resultant force corresponds to the 
direction in which the six men are pushing. 

In order that the electrical pressures produced by several batteries 
may act in the same direction around the electrical circuit, it is neces¬ 
sary that the terminal of lower electrical pressure of one battery be 
connected to the terminal of higher pressure of the next battery; 
that is, that the negative terminal of one battery be connected to 
the positive terminal of the next one. The pressure produced by the 
battery causes the electricity to pass through the battery itself from 
the terminal of lower pressure, or negative terminal, toward the 
terminal of higher pressure, or positive terminal, while in the part 
of the electrical circuit outside of the battery it causes the electricity 
to pass from the terminal of higher pressure toward the terminal of 
lower pressure. 

The action of a generator is exactly the same as the battery, inas¬ 
much as the current is from the negative to the positive terminal 
within the generator and from the positive to the negative terminal 
through the circuit outside the generator. If several electrical pres¬ 
sures be connected in series in such a manner that part of them are 
acting in one direction around the electrical circuit and the remainder 
in the opposite direction, the total pressure acting in the circuit will 
not be equal to the sum of all the different pressures, but it will be 
equal to the difference in the sums of the pressures acting in the 
opposite directions. 

The difference in the sum of the pressures acting in the two 


38 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

directions around the circuit is called the effective pressure and the 
direction of the effective pressure will correspond to the direction 
of the larger sum of pressures. For example, if six dry cells each 
producing a pressure of 1.5 volts, are connected in series, but the 
pressure produced by two of them is in the opposite direction to 
the pressure produced by the remaining four cells, then the effec¬ 
tive pressure in the circuit will be equal to the pressure produced 
by the four cells, or 6 volts, minus the pressure produced by the 
two cells, or 3 volts, which gives 3 volts. The same effective pres¬ 
sure could be produced by two cells acting alone, as the pressure 
produced by two of the six cells acting in one direction is exactly 
counteracted by the pressure of two of the six cells acting in the 
opposite direction. 

Arrangement of the Parts of a Series Circuit 

The order in which the various parts of a series circuit are 
arranged has nothing to do with the operation of the circuit. The 
pressures may be connected together at one point and the resistances 
all connected directly together, or the pressures may be distributed 
around the circuit by connecting the resistances between the differ¬ 
ent pressures. The effective pressure acting in the series circuit is 
independent of the location of the various pressures in the cir¬ 
cuit and, likewise, the total resistance of the circuit is independent 
of the location of the different resistances forming the circuit. Two 
6-volt lamps and two 6-volt batteries may be connected in series 
as shown in Fig. 20 or they may be connected as shown in Fig. 21 
and the results are exactly the same. 

If a voltmeter be connected between the points A and B in Figs. 
20 and 21 there will be no indication of pressure between the two 
points and so far as the operation of the circuit is concerned they 
may be connected together. The reason for there being no differ¬ 
ence in pressure between the points A and B is as follows: The 
same part of the total pressure is used in operating each of the 
lamps, since they are supposed to have the same resistance, and, 
since the pressure produced by each of the batteries is the same, 
we can think of one of the batteries as producing the current in 
one of the lamps and the other battery as producing the current) in 
the other lamp. 

If the lamps were of unequal resistance, in Figs. 20 and 21, and 
the pressures produced by the batteries were the same, there would 
be a difference in pressure between the points A and Bj or, if the 


THE SERIES CIRCUIT 


39 


resistances of the lamps were the same and the pressures produced 
by the batteries were unequal, there would be a difference in pres¬ 
sure between the points A and B. If, however, the resistances of 
the lamps are unequal and the pressures produced by the batteries 
are also unequal, but the relation between the resistances is the 



Figs. 20 and 21 —Two methods of connecting lamps and bat¬ 
teries in series 

♦dame as the relation between the pressures produced by the batteries, 
then there will be zero pressure between the points A and B, if these 
points are so chosen that the lamp of higher resistance is in circuit 
with the battery of higher pressure between the two points. 

Internal Resistance 

Part of the pressure produced by a pump, when it is causing the 
water to flow through a water circuit is used in causing the water 




























40 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

to flow through the pump itself. The property of the pump which 
results in part of the pressure it produces being used in the above 
manner may be called the internal resistance of the pump. The 
greater the current of water through the pump, the greater the 
pressure required to overcome the internal resistance of the pump. 

When there is no current through the pump the difference in the 
pressure indicated by two gauges connected to the terminals of the 
pumps will represent the total pressure produced by the pump. The 
part of this total pressure which is available to act on the external 
circuit and produces a current will depend upon how much of it is 
used within the pump itself. It is obvious that the pressure between 
the terminals of the pump when there is a certain current through 
it will be greater for a low internal resistance than for a high 
internal resistance. Hence, it is desirable to have the internal 
resistance of the pump as low as possible in order that just as 
much of the pressure it produces be available at the terminals of 
the pump. The pressure between the terminals of the pump will 
change as the current through the pump changes even though the 
total pressure produced by the pump remains constant. The larger 
the current through the pump the lower the difference between the 
terminal pressures. 

All of the pressure produced by the battery or generator is not 
available at the terminals, as a part of the pressure is used in 
causing the electricity to flow through generator or battery. The 
opposition offered by the generator or battery to the flow of elec¬ 
tricity through it is called the internal resistance. The action of 
the internal resistance of the generator or battery is exactly the 
same as the internal resistance of the pump. It results in the 
pressure between the terminals of the generator or battery decreas¬ 
ing as the value of the current through them increases, assuming 
the total pressure generated remains practically constant. A few 
simple examples will perhaps give the reader a better understand¬ 
ing of the effect of this internal resistance upon the operation of 
the electrical circuit. 

The total pressure generated in a certain storage battery is 6.8 
volts and the internal resistance of the battery is .04 ohm. What 
will be the pressure between the terminals of the battery when the 
battery is supplying a current of 20 amperes? 

The pressure required to produce a current of 20 amperes through 
a resistance of .04 is equal to the product of the current and the 


THE SERIES CIRCUIT 


41 


resistance, .04 X 20, or .8 volt. The pressure available at the 
terminals of the battery will be equal to the total pressure minus 
the pressure required to produce the current through the internal 
resistance, or 6.8 minus .8, or 6 volts. 

If several batteries similar to the above be connected in series 
so that their pressures are all acting in the same direction around 
the circuit there will be a decrease in the value of the pressure 
between the terminals of each of the batteries as the current in 
the circuit increases in value. The decrease in pressure of the 
different batteries will be the same provided their internal resis¬ 
tances are equal in value. If the internal resistance of the differ¬ 
ent batteries are not equal, there will be a greater decrease in the 
value of the pressure between the terminals of the batteries of larger 
internal resistance than between the terminals of the batteries of 
lower internal resistance. 

It may happen that the internal resistance of*one or more of 
the batteries is such that the pressure required to cause the electricity 
to flow through its internal resistance is greater than the pressure 
produced by that particular battery, which results in a part of the 
pressure produced by some other battery of lower internal resistance 
being used to cause the electricity to flow through the battery of 
higher internal resistance. 

This state of affairs may exist in a circuit composed of a number 
of dry cells connected in series. The pressure produced by each of 
the dry cells may be the same when measured by means of a volt¬ 
meter and there is no current through them except that required to 
operate the voltmeter. If a current be taken from each of the cells, 
it will be observed that there is a decrease in the voltmeter reading 
due to a part of the total pressure being used within the cell. The 
internal resistance of some of the cells may be such that it will be 
impossible to get a very large current from the cells even if their 
terminals be connected directly to the ammeter. A cell of high 
internal resistance may do more harm in a circuit than it does good. 

For example, when the pressure required to cause the electricity to 
flow through the internal resistance is greater than the pressure the 
cell is producing, the cell is a hindrance rather than an aid to the 
operation of the circuit. All of the cells may help in producing the 
current, when the value of the current is small, but with an increase 
in current some of the cells may prove to be worthless or a hindrance 
to the operation of the circuit. 


42 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The above discussion leads to the conclusion that the condition of 
a cell cannot be determined by measuring its pressure alone, but 
the ability of the cell to deliver current or the decrease in pressure 
between its terminals with an increased in current must be deter¬ 
mined. A more detailed discussion of the internal resistance of a 
cell will be given in the section on batteries. 

Calculating Resistance for Battery Charging 

A storage battery is charged by sending a current through the 
battery from the positive to the negative terminal or just opposite 
to the direction in which the pressure of the storage battery acts. 
The pressure producing the current must be ample to overcome 
the pressure of the storage battery and in addition to produce the 
required current through the resistance of the connecting leads and 
the internal resistance of the battery. In some cases the pres¬ 
sure producing the current is varied in value in order to produce 
the required current, while in some cases the pressure of the source 
from which the charging current is derived remains constant and the 
resistance of the circuit is adjusted so as to give the proper current. 

For example, what resistance must be connected in circuit, if 
it is desired to send 4 amperes through a 6-volt battery when it 
is connected to a 110-volt circuit? If the pressure produced by 
the battery is exactly 6 volts and the pressure of the circuit to 
which the battery is connected is 110 volts, then the effective pres¬ 
sure is equal to 110 minus 6, or 104 volts. This effective pressure of 
104 volts is to produce a current of 4 amperes, therefore the resis¬ 
tance of the circuit must be equal to 104 divided by 4, or 26 ohms. 
This resistance of 26 ohms represents the total resistance of the 
circuit. If the pressure of the battery increases, the current in the 
circuit will decrease as the effective pressure will be less. In order 
to maintain the current constant in value, as the value of the effec¬ 
tive pressure decreases, it will be necessary to decrease the resistance 
oi the circuit. 

If several batteries be connected in series, the effective pressure 
will be less than in the case of a single battery, and hence less 
resistance will be required in order that the current be the same 
in both cases. Details for charging storage batteries will be given 
in the section on batteries. 


CHAPTER III 

Parallel Circuits 

I F a water circuit is composed of two pipes and they are connected 
in the manner indicated at A and B in Fig. 22, they are said to 
be connected in parallel or multiple. There are two paths in which 
the water may flow in passing along the circuit from the point A 
to the point B and just as much water is returning to the pump 
in a given time as is leaving it. The quantities of water passing 
through the different pipes in a given time or the currents of water 
in the different pipes connected in parallel are not necessarily equal 
unless the resistances of the different pipes are the same. The 
water is not used up in the operation of such a circuit. 

An electrical circuit composed of two or , more different wires 
of perhaps different sizes, lengths and material, and connected as 
shown in Fig. 23, is called a multiple or parallel circuit. In this 
case there are as many paths for the electricity to flow through 
in passing from the positive terminal to the negative terminal, 
through the circuits outside the battery, as there are different 
wires in parallel. Just as much electricity is returning to the 
battery in a given time as is leaving the battery. The quantities 
of electricity passing through the different paths in one second 
or the currents in the different paths of the parallel circuits are 
not necessarily equal unless the resistance of the different paths is 
the same. Just remember that the electricity is not used up in the 
operation of such a circuit. 

A parallel water circuit is found in the operation of the cool¬ 
ing system of a motor car engine, as shown in Fig. 24. In this 
case, the water jackets of the four cylinders are all connected in 
parallel and the pump forces the water through the water jackets 
and radiator. The current of water through the pump and radiator 
is the same and equal to the combined currents through the four 
water jackets. The currents in the different water jackets are not 


44 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

necessarily equal unless the opposition offered to the flow of water 
through the different jackets is the same in each case. It is obvious 
that, if the water jacket of one cylinder offers a greater opposition 
to the flow of the water than the other water jackets, there will be 
a smaller current through this jacket than through the others. 









* 

* 




•• * • ’ > 




LuvuXwu V 


% 





Fig. 22 —A parellel renter circuit 



The water jacket offering the greatest opposition to the flow of 
water will have the smallest current; while the water jacket offering 
the smallest opposition always will have the largest current. The 
current in the remaining paths will have a value somewhere between 
the above maximum and minimum values. 
















































PARALLEL circuits 


45 


When the headlights on a motor ear are connected as shown in 
Fig. 25, they form a typical parallel electrical circuit. Just as 
much electricity returns to the battery in a given time as leaves 
the battery. The current in each of the lamps is not necessarily 
the same. Remember the electricity is not consumed in the lamps. 



Fig. 24 —Parallel water circuit in car’s cooling system 



Resistance of Parallel Circuits 

Since the resistance offered by a pipe to the free flow of water 
through it decreases with an increase in the size of the pipe the 
length remaining constant, it is evident that the resistance offered 
by two pipes connected in parallel will be less than the resistance 















































46 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of a single pipe. If the two pipes are of exactly the same size 
and length, they will, when connected in parallel, offer one-half of 
the resistance to the flow of water through the circuit that is offered 
by a single pipe. 

For convenience, the two pipes, as shown in Fig. 26, might be 
considered as being equivalent to a single pipe, as shown in Fig. 
.27, whose length is the same as that of each of the two pipes and 
whose area is equal to the combined area of the two pipes, which 
will be twice that of either pipe, since the pipes are equal in area. 
The resistance of this large pipe, which is to replace the two 



ance as one pipe, at left, if the combined areas of the two small 
pipes are equal to the area of the large pipe 

smaller ones, will be one-half of that of either of the single small 
pipes since its area is equal to twice the area of either of the two 
small pipes. 

Two wires of the same size and length and of the same material 
will, when connected in parallel, offer a resistance which is equal 
to the resistance of a wire of the same material and having the 
same length but having an area equal to twice the area of either 
wire. Thus the resistance of two wires of the same dimensions and 
material will offer, when connected in parallel, one-half of the 
resistance of - either wire alone. Any number of electrical resist¬ 
ances connected in parallel might be thought of as being equivalent 
to a number of wires of the same length and material but having 










PARALLEL CIRCUITS 


47 


the same or different areas. Their combined resistance then will 
be equal to the resistance of a single wire of the same material 
and same length and whose area is equal to the sum of the areas 
of the several different wires. 

For example, if two resistances of 6 and 3 ohms, respectively, be 
connected in parallel, their combined resistance may be determined 
as follows: 

For convenience, let us assume that these two resistances are two 
wires of the same material and that they are equal in length. Then, 
the area of the 3-ohm wire will be twice the area of the 6-ohm wire, 
since its resistance is one-half as great, the area increasing as the 
resistance decreases. The two wires will have a combined area 
equal to three times the area of the 6-olim wire. The resistance 
of a wire whose area is three times that of another wire of the 
same material and having the same length will be one-third of the 
resistance of the smaller wire. 

Hence, the resistance of a wire which may replace the two wires 
is equal to one-third the resistance of the 6-ohm wire, or 2 ohms. 

Suppose three resistances of 4, 3 and 12 ohms, respectively, be 
connected in parallel. Their combined resistance may be deter¬ 
mined as follows: 

Again let us assume that these resistances are three wires of the 
same material and all have the same length, then the area of the 
4-ohm wire will be three times as great as the area of *the 12-ohm 
wire and the area of the 3-ohm wire will be four times as great 
as the area of the 12-ohm wire. 

The three wires will have a combined area equal to 1 + 3 + 4 
or 8 times the area of the 12-ohm wire. This equivalent wire whose 
area is 8 times the area of the 12-ohm wire will have a resistance 
equal to one-eighth of the 12-ohm wire or 1 y 2 , ohms. 

Any number of resistances may be combined in the above manner 
by first assuming them all composed of the same material and having 
the same length and then replaced by a wire of the same material 
and same length, but having an area equal to the combined area 
of the several wires. 

Conductance 

The resistance of the electrical circuit is a property of the cir¬ 
cuit which opposes the free flow of electricity through the circuit, 
and it is measured in a unit called the ohm. The property of the 
circuit which permits the electricity to flow, or that property which 


48 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

is just the opposite of resistance and is equal to 1 divided by the 
resistance in ohms, is called the conductance of the circuit and 
it is measured in a unit called the mho. It is interesting to note 
that the unit in which the conductance is measured is the unit of 
resistance, the ohm, spelled backward. 

The resistance of a parallel circuit may be determined by merely 
adding the conductances of the several parts just as the resistance 
of a series circuit may be determined by adding the resistances 
of the different parts. For example, if two resistances of 6 and 3 
ohms, respectively, are connected in parallel their resistance may be 
determined as follows: The conductance of the 6-ohm branch 
will be equal to 1. divided by 6, or 1/6 mho, and the conductance 
of the 3-ohm branch will be equal to 1 divided by 3, or % mho. 
The total conductance of the divided circuit will be equal to the 
sum of the conductances of the two branches, or 

total conductance = 1/6 + 1/3 = 3/6 mho 

Since the conductance of a circuit is equal to 1 divided by the 
resistance then the above relation may be written as follows: 

1 

-TT-= 3/6 

resistance 

or the resistance = 6/3 = 2 ohms 
Suppose three resistances of 6, 3 and 12 ohms, respectively, be 
connected in parallel, then their combined resistance may be deter¬ 
mined as follows: 

total conductance = + ft + % 

= ft + ft + ft 

= ft mho 

1 

Then -= ft 

resistance 

or the resistance = ft = 1 y 2 ohms 

If two headlights whose resistance are 4 and 2 ohms respectively 
be connected in parallel, what will be the value of their combined 
resistance? The conductance of the two branches of the divided 
circuit formed by the two lamps will be one-fourth and one-half 
mho respectively, and the total conductance will be 




PAikii^L CIRCUITS 


49 


total conductance = ^4 + %i 

= % + % 

= % mho 

1 

then- 7 -—= % 

resistance 

or, the resistance = % = iy 3 ohms 

Therefore the two lamps will have a combined resistance of 1 % 
ohms. 

When any number of equal resistances are connected in parallel 
the total resistance is equal to the resistance of one of the resistances 
divided by the number of resistances connected in parallel. For 
example, if six 4-ohm lamps are connected in parallel the total 
resistance of the combination will be equal to 4 divided by 6 , or 
% ohm. Remember this method of determining the resistance of a 
parallel circuit holds true only when the value of the different re¬ 
sistances is the same. 

Pressure Relations for the Parallel Circuit 

If pressure gauges be connected to the water circuit at the points 
A and B as indicated in Fig. 28, the difference in the readings of 
the two gauges will represent the pressure acting on each of the 
pipes forming the parallel circuit. It is obvious, from an inspec¬ 
tion of this figure, that the pressure acting on each of the branches 
of a parallel or divided circuit is at each instant exactly the same. 

If a voltmeter be connected to the electrical circuit at the points 
A and B as indicated in Fig. 29, the pressure indicated by the volt¬ 
meter will represent the value of the pressure acting on the divided 
circuit, and, it is obvious that the pressure acting on each of the 
several branches of a parallel circuit at any instant is exactly the 
same, since each branch is connected between the same two points. 
If several lamps be connected in parallel, the pressure acting on 
each of the lamps will be the same regardless of their candle-power 
or voltage ratings. 

Current Relations for the Parallel Circuit 

If two pipes of the same size and same length be connected in 
parallel and the combination in turn connected to a pump, the 
current of water in each of the pipes will be the same since they 



50 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


each offer the same resistance and the same pressure is acting on 
each of them. If, however, one of the pipes be longer than the 
other, their size being the same; or if one pipe be smaller than the 
other, their lengths being the same, the current of water in the two 
pipes will not be the same. The current of water in the pipe which 



> 


* 


















/ 1 1 








Fig. 28 —The difference of the 
readings of the two pressure 
gauges at either end of the 
parallel water circuit represents 
the pressure on each pipe 


Fig. 29 —The voltmeter across the 
ends of the tranches in a parallel 
electric circuit shows the pressure 
in each branch 3 since the pressure 
is the same in each branch 


offers the greater resistance will be less than the current of water 
in the pipe which offers the less resistance. For example, if the 
resistance of one pipe is twice as great as the resistance of the 
other pipe, then the current in it will be one-half as great as the 
current in the other pipe. 






























PARALLEL CIRCUITS 


51 


If two equal electrical resistances be connected in parallel they 
will each carry the same current. For example, if two 12-volt 
headlights of the same make and same candlepower be connected in 
parallel to a 12-volt battery, the current in each of the lamps will 
be practically the same. The total current supplied' by the battery 
will be equal to the sum of the currents in the two branches. If, 
however, two resistances which are unequal in value be connected 
in parallel the current in the resistances will not be the same. 

The branch of the divided circuit having the larger resistance 
w r ill carry the smaller current, while the branch of the divided cir¬ 
cuit having the smaller resistance will carry the larger current. The 
total current supplied to the divided circuit will be equal to the 
sum of the currents in the two branches regardless of whether these, 
are equal or not. Thus if two 6-volt lamps which take currents or 
3 and 2 amperes respectively be connected in parallel to the 
terminals of a 6-volt battery, the total current taken by the lamps 
will be equal to 3 plus 2 or 5 amperes. 

From the above discussion it is obvious that lamps made to 
operate on different voltages can not be operated satisfactorily in 
parallel, because, if the voltage is adjusted to the proper value 
for one lamp, it is not correct for the other. In the case of the 
series circuit, the lamps had to take the same current in order to 
operate satisfactorily in series. 

The relation of the currents in the two branches of a divided 
circuit is just the reverse of the- relation between the resistances 
of the two branches. Thus, if the resistances of the two branches 
of a divided circuit are 4 and 8 ohms, respectively, then the current 
in the 4-ohm branch will be twice as great as the current in the 
8 -ohm branch since the resistance of the 4-ohm branch is one-half 
the resistance of the 8-ohm branch. 

The total current supplied to a parallel circuit of any number 
of branches is equal to the sum of the currents in all of the differ¬ 
ent branches, and the relation of the currents in the different 
branches is just the reverse of the relation of the resistance of the 
different branches. 

Examples Illustrating Relations of Parallel Circuits 

If three resistances of 6, 3 and 2 ohms respectively are con¬ 
nected in parallel the relation of the currents in the different 
branches will be as follows: The current in the 2-ohm resistance 


52 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

will be equal to three times the current in the 6-ohm resistance and 
one and one-half times the current in the 3-ohm resistance. The 
current in the 3-ohm resistance will be equal to twice the current 
in the 6-ohm resistance and two-thirds of the current in the 2-ohm 
resistance. The current in the 6-ohm coil will be equal to one-half 
of the current in the 3-ohm coil and one-third of the current in the 
2 -ohm coil. 

The resistance of the winding of an electric heater which is made 
to operate on a 12-volt battery is 3 ohms. What will the resistance 
of this heater be if a second winding of 6 ohms is connected in 
parallel with the first winding and what current will the heater 
take from a 12-volt battery after the second winding is put in place? 

The combined conductance of the two windings is equal to 


1 /3+y 6 =%+ 1 / / 6=%mho 


then the resistance will be equal to 6 divided by 3, or 2 ohms. 

The current taken by the 6-ohm. winding will be equal to 12 
divided by 6 or 2 amperes, and the current taken by the 3-ohm 
winding will be equal to 12 divided by 3 or 4 amperes. The total 
current taken by the heater after the second winding is put in 
jjlace, will be equal to the sum of the currents taken by the two 
windings, that is 2 + 4 or 6 amperes. 

The total current can be obtained by dividing the pressure acting 
on the heater by the combined resistance of the two windings, as 
follows: 

12 

I = — =6 amperes 
2 

Combined Series and Parallel Circuits 

An electrical circuit may be a combination of one or more series 
and parallel circuits, as shown in Fig. 30, which represents two 
headlights in parallel with each other and this combination in turn 
connected in series with a resistance R and a storage battery. This 
is the principle used in some methods of dimming headlights. The 
sum of the currents through the two lamps is equal to the total 
current or the current in the resistance. The total resistance of this 
circuit is equal to the sum of the resistance of the parallel portion 
and the resistance of the remainder of the circuit. For example. 


PARALLEL CIRCUITS 


53 


if the resistance of the two lamps is 4 ohms each and the resis¬ 
tance of the coil in series is 3 ohms, the total resistance can be 
determined as follows: 

Since the two lamps have equal resistances, their combined resis¬ 
tance will be equal to 4 divided by 2 or 2 ohms, and the total 

resistance will be equal to 2 plus 3 or 5 ohms. 

If the voltage of the battery is 6 volts, the current in the 

circuit will be equal to 6 divided by 5 or 1.2 amperes. The value 
of the current in each of the lamps will be the same, since the two 
paths of the divided circuit have the same resistance, or one-half 
of 1.2, or .6 ampere. The pressure over the two lamps in parallel 
will be the same part of the total pressure as the resistance of the 
two lamps in parallel is a part of the total resistance. The resis¬ 
tance of the two lamps in parallel is 2 ohms and the total resistance 
is 5 ohms. Hence, the pressure over the lamps will be equal to % 
of 6 or 2.4 volts. 

The pressure over the 3-ohm resistance will be equal to % of 6 
or 3.6 volts. Or, if the drop over one part of the circuit is known 
the drop over the other part will be equal to the total pressure minus 
the drop over the first part. Thus the drop over the two lamps in 
parallel is 2.4 volts. Then, the drop over the 3-ohm resistance will 
be equal to 6 minus 2.4 or 3.6 volts. 

Pressures in Parallel 


If two pumps be connected, as shown in Fig. 31, they are said to be 
connected in parallel and the sum of the currents of water through 
the two pumps will be equal to the total current in the main pipes 



Fig. 30 —A combined series and parallel lighting circuit, in which 
the lamps are in parallel and a resistance coil in series with the 

battery 
















54 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

and water motor M, provided the currents in the two pumps are 
both in the same direction, that is, say from the point A to the 
point B, as indicated. 

Let us assume that the valve Y in the main circuit is closed so 
that there is no current through the water motor M. If the pres¬ 
sures produced by the two pumps are exactly equal and in the same 
direction with respect to the junction points A and B in Fig. 31, 
there will be no current through either pump because the two pres¬ 
sures are equal and neutralize each other. If, however, the pres¬ 
sure produced by one pump is less than that produced by the other 
pump, the two pressures no longer neutralized and there will be a 
current produced through both pumps by an effective pressure which 



Fig. 31 —Water pressures in parallel. Two pumps, PI and P2, 
supply one motor M 


will be equal to the difference in the pressures produced by the 
respective pumps. 

For example, suppose the pressure produced by the upper pump 
is less than the pressure produced by the lower pump, then there 
will be an effective pressure acting around the circuit composed 
of the two pumps and their connecting pipes in the direction of 
the arrows through P2. 

The current in the upper pump will be in a direction through 
that pump opposite to the direction of the pressure the pump itself 



























PARALLEL CIRCUITS 


55 


is producing; while in the lower pump the direction of the current 
will be the same as the direction of the pressure that pump is pro¬ 
ducing. The current will be in the same direction as the arrows 
through PI if the pressure produced by the upper pump is greater 
than the pressure produced by the lower pump. 

The pressure between the two points A and B will be equal to 
the pressure produced by either or both pumps, provided there is 
no current in either or both of the pumps. When there is a current 
through either or both of the pumps and if this current is in the 
same direction as the pressure produced by the pump, the pres¬ 
sure between the terminals of the pump or between the points 
A and B will be equal to the total pressure produced by the pump 



Fig. 32 —Electrical pressures in parallel. Two batteries supply 

one lamp 

less the pressure required to force the water through the circuit 
between the points A and B or to overcome the internal resistance 
of the pump. 

If the current through the pump is in the opposite direction to 
the pressure produced by the pump, the pressure between the 
terminals of the pump or between the points A and B will be equal 
to the total pressure produced by the pump plus the pressure re¬ 
quired to force the water through the circuit between the point 
A and the point B or to overcome the internal resistance of the 
pump. 





















56 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

It is obvious from the above discussion that the operation of 
two pumps having different internal resistances and producing differ¬ 
ent pressures would not be very satisfactory. 

Two batteries are shown connected in parallel in Fig 32 and 
arranged to supply current to a 6-volt lamp. When the electrical 
pressure produced by the tw T o batteries is the same and the two 
positives are connected together and the two negatives together, 
there will be no current through either of them when the switch S 
in the main circuit is open. If, however, the pressure produced by 
one battery is greater than that produced by the other, then there 
will be a current through both batteries when the outside circuit is 
open. 

Suppose, for example, the pressure produced by the lower battery 
is greater than the pressure produced by the upper battery. Then, 
there will be a current through the upper battery in a direction 
opposite to its own pressure, even though there be no current in the 
main circuit. If the value of the current in the main circuit be 
increased gradually there will be a decrease in the terminal pressure 
of the batteries, but the one of higher pressure will send a cur¬ 
rent through the one of lower pressure and also the current through 
the main circuit. 

As the current in the main circuit increases, the terminal pres* 
sure of the batteries will continue to decrease and finally this pres¬ 
sure will be equal to the pressure produced by the upper battery. 
Then, there will be no current through the upper battery. While 
there is a current through the upper battery in a direction opposite 
to its own pressure, the battery is doing more harm than good, so 
far as the main circuit is concerned. If the current in the main 
circuit further increases, the terminal pressure between the points 
A and B will decrease and there will be a current in the upper 
battery in the same direction as the pressure of that battery. 

Suppose two batteries whose pressures are 6.5 and 7 volts, respec¬ 
tively, and whose internal resistances are .01 and .015* .ohm, respec¬ 
tively, are connected in parallel as indicated in Fig. 32. What 
current will there be in each battery, when the main circuit is open? 

The pressures produced by the two batteries are in opposition 
to each other, but they will not be neutralized, as they are not 
equal in value, and, as a result, there will be an effective pressure 
acting in the circuit, composed of the two batteries and their 
connecting leads, equal in value to the difference between the pres- 


PARALLEL CIRCUITS 


57 


sures of the two batteries, which is equal to 7.0 minus 6.5 or .5 volt. 
Neglecting the resistance of the connecting leads, this effective 
pressure is acting in a circuit whose combined resistance is equal 
to the sum of internal resistances of the two batteries, which is 
.010 plus .015 or .025 ohm. There will be a current produced whose 
value is equal to the effective pressure divided by the resistance, or 

current = .5 -r- .025 — 20 amperes. 

Hence, the 7-volt battery will charge the 6.5-volt battery at a 
20 -ampere rate, when there is no current in the main circuit. 

The current in the 6.5-volt battery will be zero when the terminal 
voltage of the 7-volt battery is 6.5 volts. In order that the terminal 
voltage of the 7-volt battery be 6.5 volts, .5 volt must be used within 
the battery itself in overcoming the internal resistance of the 
battery. This .5 volt pressure will produce a current whose value 
is equal to this pressure divided by the internal resistance of the 
battery, or 

current = .5 -f- .015 = 33% amperes. 

Hence, the current in the 6.5-volt battery will be zero when the 
current in the main circuit is 33% amperes. The 6.5-volt battery 
will be charging from the 7-volt battery for all values of current 
in the main circuit up to 33% amperes. When the current in the 
main circuit exceeds 33% amperes, both batteries act together to 
produce a current in the main circuit, but the value of the current 
through them is not the same. 

If the pressures produced by two batteries connected in parallel 
are equal but their internal resistances are unequal, they will not 
each carry the same value of current, but the one of lower internal 
resistance always will carry the larger part of the total current. 
The reason for this is that the terminal voltages of the two bat¬ 
teries always are equal when the two batteries are connected in 
parallel, and, in order that this be the ease when there is a current 
through them and their total pressures are equal, it is necessary 
that the battery of lower internal resistance carry a larger current 
than the one of higher internal resistance so that their internal 
drops will be equal. 

The above relations readily account for the fact that two bat¬ 
teries will not always operate satisfactorily in parallel as it is really 
necessary that they have the same internal resistances and produce 
the same pressures in order that they divide the total current 
equally for all values of the current they may have to supply. Thq 
same thing is true of dry cells, 


CHAPTER IV 


Making Electricity Do Work 

Force 

I N general terms, a force is that which produces, stops, changes, 
or tends to produce, stop, or change the motion or rest of a 
body. Thus, a force always must be applied to a body to cause it 
to move, as when you push on a car, and a force must be applied 
in order to increase or decrease the velocity of a body that is in 
motion. A force does not always produce motion, but may only 
tend to produce it, as when you push on a brick wall you apply a 
muscular force, but there is not necessarily any movement of the 
wall. 

There are a number of different kinds of force, some of the most 
common of which are as follows: gravitational force, as a result of 
which all bodies fall from a higher to a lower level; mechanical 
force, which may be produced by the explosion of a gas mixture in 
the cylinder of the gas engine; electrical force, which produces or 
tends to produce a movement of electricity in the electrical circuit; 
etc. The electrical force is commonly produced by chemical action in 
the battery or by means of an electrical generator. 

An electrical force is measured in volts, while other forces are 
usually measured in pounds. 

Work 

If a force overcomes a certain resistance, vrork is done; or work 
is the result of the action of a force through a certain distance. 
Work is measured in a unit which is a combination of the unit in 
which the force is measured and the unit in which the distance is 
measured. For example, if you push on a car with a force of 75 
pounds and the car moves through a distance of 200 feet, as show* 
in Fig. 33, the work done will be equal to the product of the value 
of the force and the distance through which the force acts, or 
75 X 200 = 15,000 foot-pounds. 


MAKING ELECTRICITY DO WORK 


59 


It must be clearly understood that a force may exist without 
work being done, as, when you shove on a wall, you do no work 
unless there is an actual movement as a result of the force. 

If a man carries 100 pounds of material from one floor of a 
building to another floor which is 50 feet above the one from 
which he started, he will do 100 times 50 or 5,000 foot-pounds of 
work. 

A man would do the same amount of work in carrying 200 pounds 
of material up a height of 25 feet, 50 pounds up a height of 100 
feet, etc. 

If a pump raises 1,200 gallons of watc-r a vertical height of 100 
feet and each gallon weighs 8% pounds, the work done by the 
pump will be equal to the weight of the water raised, multiplied by 
the distance through which it is raised. The weight of the water 



i'T ^ ^ 

Fig. 33 —Force overcoming distance. If the car is gushed hy a 
force of 75 pounds a distance of 200 feet the work done will 
equal 15,000 foot-pounds 

raised in this particular case is equal to 1,200 X 8% = 10,000 
pounds, and since this weight of water is raised 100 feet, the work 
done will be equal to 10,000 X 100 = 1,000,000 foot-pounds. 

The same amount of work would be done in raising 600 gallons 
to a height of 200 feet, 2,400 gallons to a height of 50 feet, etc. 

A motor car weighing 5,000 pounds is to be raised from the 
ground floor of a building by means of a freight elevator, as shown 
in Fig. 34, to one of the upper floors which is 50 feet above the 
ground floor. Assuming that the elevator is properly counter¬ 
balanced, and neglecting the friction of the guides, pulleys, ropes, 
etc., what will be the value of the work done in raising the car to 
the upper floor? The actual work done in raising the car. is equal 
to the weight of the car multiplied by the distance through which 
it is raised, namely 5,000 X 50 = 250,000 foot-pounds*. 

The same amount of work would be done in raising a car weigh- 



60 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ing 6,000, a vertical distance of 25 feet; in raising one weighing 
1,500 pounds, a vertical distance of 100 feet, etc. 

A disabled car is being drawn by a second car at a constant 
speed on a level street and a spring balance which is connected in 
the tow rope, as shown in Fig. 35, indicates a pull of 100 pounds. 



Fig. 34 —Illustrating the value of the work 
done in raising a 5,000-pound car 50 feet 


The work done in pulling this car a distance of 2 miles is equal 
to the distance in feet multiplied by the pull on the car, or 2 X 5,280 
(or 10,560 feet) multiplied by 100 or 1,056,000 foot-pounds. 

The same amount of work would be done in drawing a disabled 
car 1 mile, if the pull on the tow rope was 200 pounds; in drawing 
a car 4 miles, if the pull at the tow rope was 50 pounds, etc. 

If a unit quantity of electricity, or 1 coulomb, is moved from some 
point on an electrical circuit to another point on the circuit whose 
electrical pressure is 1 volt higher than the first point, 1 unit of 
electrical work will be done upon the quantity of electricity which 
is moved. . This unit of electrical work is called the joule. The 
quantity of electricity in coulombs passing through a circuit in a 


























































MAKING ELECTRICITY DO WORK 


61 

certain time is equal to the product of the steady current in amperes 
and the time in seconds. For example, if a storage battery, when 
being charged takes a current of 4 amperes, the quantity of elec¬ 
tricity passing through the battery in 1 hour, or 3,600 seconds, will 
be equal to 4 X 3,600, or 14,400 coulombs. If the pressure between 
the terminals of the battery is known, then the work done in 
charging the battery for 1 hour will be equal to the product of the 
quantity of electricity and the value of the difference in electrical 
level through which it is raised. Hence the work done in this par¬ 
ticular case is equal to 14,400 X 7, or 100,800 joules. 



Fig. 35 —Determining the work done in towing a car when the 
pull is 100 pounds 


The same amount of work would be done in charging a battery 
if the current were 2 amperes and the battery were on charge for 2 
hours; if the current were 1 ampere and the battery were on charge 
4 hours, etc. Likewise, the same amount of work would be done 
if the current were 8 amperes the pressure were 3.5 volts and the 
battery was on charge for 1 hour; if the current was 2 amperes, 
the pressure 14 volts and the battery was on charge 1 hour, etc. 

What is the work done in operating a starting motor for 2 minutes 
if it takes a current of 150 amperes from a 6-volt battery? 

The quantity of electricity moved is equal to the time in seconds, 
which is 60 X 2, or 120 seconds, multiplied by the current in 
amperes. 

Quantity is 120 X 150 = 18,000 coulombs. 

The work done will be equal to the product of the electrical 
pressure and the difference in electrical level through which the 
electricity moves, or 18,000 X 7, which is equal to 126,000.joules. 

In this case, the electricity does work as it passes through the 
motor because it is passing from a point of higher electrical pressure 


















62 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

to a point of lower electrical pressure, or it is running clown hill 
electrically. 

The same amount of work would be done in operating the motor 
for 4 minutes if it took a current of 75 amperes, in operating it for 
1 minute if it took a current of 300 amperes, etc. 

Energy 

Energy may be defined as the ability to do work. Thus the 
energy of a certain quantity of water standing in a pool in the 
street is zero with respect to the street level as it is not capable 
of operating a water wheel or any other device when such a device 
is on the same level as the water. If the water contained in this 
pool be raised to the roof of a building, the water then possesses 
some energy with respect to the level of the street and is capable 
of operating a water wheel or any other device when such a device 
is on the street level, or located at any point below the level of the 
water. The energy possessed by the water with reference to the 
street level when it is raised to the top of the building is equal to 
the work done in raising the water from the street level to the top 
of the building. 

For example, when 1,200 gallons of water is raised to the top 
of a building which is 100 feet above the level of the street, the 
work done, we found in the previous section, was 1,000,000 foot¬ 
pounds. The energy possessed by this water then is 1,000,000 foot¬ 
pounds and it will do that amount of work if allowed to fall to the 
street level 100 feet below. You can think of work as being the 
expenditure of energy and energy, of course, is the ability to do 
work. The energy possessed by 600 gallons of water which has 
been raised a vertical height of 200 feet, 2,400 gallons of water 
which has been raised 50 feet, etc., is the same as the energy 
possessed by the 1,200 gallons which has been raised 100 feet. 

In the case of the car, the work done in raising it a vertical 
height of 50 feet was 250,000 foot-pounds, and the energy of the 
car when it is on the upper floor, 50 feet above the ground floor, 
is 250,000 foot-pounds with respect to the ground floor. If the 
car be placed on the elevator and allowed to descend to the ground 
floor it may be made to do just as much work, such as lifting the 
counterweight, as was done upon it in raising it to the upper floor, 
neglecting losses of all kinds. 

The work done in drawing the disabled car we found to be 1,056,- 
000 foot-pounds, but the energy possessed by the car at the end 


63 


MAKING ELECTRICITY DO WORK 

of the journey was no different from what it was at the beginning, 
because the car was drawn along a level path. All of the work 
done on the car is used in overcoming the friction of the various 
parts. As a result, no energy is stored, as in the case of the water 
which was raised to the top of the building and the car which was 
raised in the elevator. If the car had been drawn up a grade instead 
of along a level path, all of the work done on the car would not 
be used in overcoming the friction of the various parts but a part 
would be used in raising the car as it proceeds up the grade. 



Figs. 36 and 37 —Comparing the closed water circuit and the 
electrical circuit 


The part of the work done in raising the car will represent the 
difference in the energy stored in the car in the final position and 
first position. The energy stored in the car when it is raised in 
passing along the road assists the movement of the car in passing 
down a grade to the same level from which it started. If no energy 
be lost in applying the brakes and the car starts and ends at the 
same level, the same amount of work will be done in moving it 
along a level road as is done in moving it along an up and down 



























64 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

road, as the energy stored in the car as it goes up hill will be used 
when it goes down grade. 

The energy of a certain quantity of electricity at a given point 
in an electrical circuit with respect to a second point in an electrical 
circuit is equal to the work done in raising the quantity of 
electricity from the second point to the first. Thus, in the case 
of the storage battery, as given in the previous section, the work 
done was 100,800 joules and this represents the energy stored in 
the battery, assuming that all of the work done is used in pro¬ 
ducing a reverse chemical action in the battery. As a matter of 
fact the work done in charging the battery will be greater than the 
energy stored in the battery as some work done will be used in 
overcoming the internal resistance of the battery. 

The work in operating the starting motor will be transformed 
into mechanical work and may turn the engine, or do other kinds of 
work. If the motor turns the engine there will be no energy stored, 
but if it raises a weight part of the w T ork it does will overcome the 
friction of the mechanism it is driving and part of the work will 
be used in raising the weight. 

The work done in raising the weight will represent the value of 
the energy possessed by the weight in its second position with 
respect to its first position. This stored energy may be used in 
doing work. 

Comparison of the Water and Electrical Circuits 

A comparison of the operation of the closed water c : rcuit, shown 
in Fig. 36, and the electrical circuit, shown in Fig. 37, will be of 
interest inasmuch as they are quite similar. 

The water circuit consists of a pump connected in series with a 
water motor by means of several pipes and the circuit is controlled 
by the valve. The pipes, pump and motor are supposed to be filled 
With water and when the valve is open there is a flow of water in 
the circuit, just as much water returns to the pump as leaves it, 
just as much water leaves the motor as enters it; in fact, the current 
of water is exactly the same at every point in the circuit at any 
instant. Remember, the water is not used up. 

The electrical circuit consists of a generator connected in series 
with an electric motor by means of several wires and the circuit 
is controlled by means of the switch. The generator does not create 
electricity but merely produces the pressure which tends to cause 
the electricity to move through the circuit. The same quantity of 


making electricity do work 


G5 


electricity leaves the generator as enters it, the same quantity of 
electricity leaves the motor as enters it, in fact, the current of 
electricity is exactly the same at every point in the circuit at any 
instant. Remember, the electricity is not used up. 

If the water is not used up in the water motor and the electricity 
is not used up in the electric motor, what is it then that causes the 
water and electric motors to operate in their respective circuits? 
The pump causes the water to flow from a point of low pressure to 
a point of high pressure as the water passes through the pump and, 
in so doing, imparts energy to the water. The energy possessed 
by the water as it leaves the pump is greater than the energy it 
possesses when it enters the pump and, as a result, the water is 
capable of doing work as it passes through the circuit outside the 
pump. This energy or ability to do work possessed by the water 
is used in causing the water to flow through the pipes and in operat¬ 
ing the water motor. 

The generator in the electrical circuit causes the electricity to 
pass through the generator f<om thf terminal of lower electrical 
pressure to the terminal of higher electrical pressure and in so 
doing imparts energy to the electricity. The energy possessed by 
the electricity as it leaves the generator is greater than the energy 
it possesses when it enters the generator and, as a result, the elec¬ 
tricity is capable of doing work as it passes around the outside 
circuit. This energy or ability to do work possessed by the elec¬ 
tricity is used in causing the electricity to flow through the wires 
and in operating the electric motor. 

High- and Low-Pressure Circuits 

The pressure produced by the pump in Fig. 36 may be high, 
low or what might be called a medium value. If the pressure is 
low, a relatively large quantity of water must pass through the 
pipes in a given time in order to operate the water motor; while, 
if the pressure is high, the quantity of water that must pass 
through the pipes in a given time is relatively small. The energy 
possessed by the water when it is acting under a high pressure is 
greater than when it is acting under a low pressure and hence a 
certain quantity of water in a high-pressure system is capable of 
doing more work than a like quantity in a low-pressure system. 
The current in the high-pressure circuit will be less than the current 
in the low-pressure circuit. 

A similar relation exists in the electrical circuit between the quan- 


66 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

tity and pressure. That is, the higher the pressure the less the 
quantity of electricity required to do a certain amount of work 
and the lower the pressure, the larger the quantity to do the same 
amount of work. Since there is a smaller quantity of electricity 
required in the high-pressure circuit than in the low-pressure circuit 
in order to do a certain amount of work, and assuming the length 
of time required to do this work is the same in both cases, it is 
obvious that the current of electricity in the high-pressure circuit 
will be less than the current of electricity in the low-pressure cir¬ 
cuit, just as the current of water in the high-pressure water circuit 
will be less than the current of water in the low-pressure water 
circuit. 

The high-pressure electrical circuit must be insulated or better 
protected electrically than the low-pressure electrical circuit, just 
as the walls of the pipes in the high-pressure water circuit must 
be stronger than the walls of the pipes in the low-pressure water 
circuit. 

Conservation of Energy 

The amount of energy in the universe is always the same, but it 
assumes many different forms and it is possible for us to transform 
certain kinds of energy into other kinds of energy. A good example 
of the transforming process is found in the operation of the steam 
engine and generator. We start with the energy stored in the coal 
or other fuel and a part of this energy is used in heating the water 
in the boiler and thus producing a steam pressure. A part of the 
energy possessed by the steam is transformed into mechanical 
energy in the engine which drives the generator. In the generator, 
a part of the mechanical energy used in driving it is transformed 
into electrical energy. 

The electrical energy produced by the generator may be used in 
charging a storage battery where a part of it will be transformed 
into chemical energy; it may be used in operating an electric heater 
where a part of the electrical energy is transformed into heat 
energy; it may be used in operating an electric motor where a 
part of the electrical energy is transformed into mechanical energy 
and may be used in driving a pump, starting the gasoline engine, 
operating a fan, etc.; it may be used in operating an incandescent 
or arc lamp where a part of it is transformed into radiant or light 
energy, etc. 

In the operating of the gas engine, we start with the energy 


MAKING ELECTRICITY DO WORK 

stored in the fuel which may be a gas or liquid and a part of this 
energy is transformed into mechanical energy which may be used 
in driving the motor car, the charging generator, circulating pump, 
etc. You see numerous examples every day in which these or 
other transformations of energy are taking place. 

The all-important point to remember is that we are not creating 
or destroying energy but merely transforming it from one lcind to 
another which will better serve our purpose. 

In general, there are two kinds of energy and these are called 
potential and lcinetic energy, respectively. Potential energy is the 
energy due to position or condition as, for example, the energy 
possessed by a certain quantity of water with respect to the ground 
level when the water is located on a level above the ground; the 
energy possessed by the volume of water held behind the dam above 
the water wheel; the energy possessed by a. steel spring after it 
has been put under a strain, perhaps elongated, compressed, or 
bent out of shape; the energy possessed by a quantity of air stored 
in a pressure tank; or a pneumatic tire, etc.; the energy stored in 
the primary or secondary battery; the energy stored in the coal, 
gasoline, gas, wood, etc., and numerous other examples. 

Kinetic energy is the energy of a body due to its motion as, for 
example, a car in motion; the energy stored in a fly wheel when it 
is turning; the energy stored in a stone or other body when it is 
falling, etc. 

In throwing a baseball up in the air, the following transforma¬ 
tions take place. We start with potential energy stored in the 
individual who is going to throw the ball, and a part of this energy 
is imparted to the ball and it is in the form of kinetic energy as the 
ball leaves the pitcher’s hand. This kinetic energy is transformed 
into potential energy as the ball goes up into the air and finally 
it possesses no kinetic energy just at the instant it is neither going 
up or down. The potential energy is then transformed into kinetic 
energy as the ball descends and the greater part of this kinetic 
energy will be transformed into heat energy when the ball strikes 
in the glove or hands of the catcher. 

In the various transformations of energy from one kind to 
another, the transformation is not altogether complete; that is, it 
never is 100 per cent efficient. Some of it always will be trans¬ 
formed into some other form which we do not want, usually heat. 
For example, the electrical energy from a battery which is coil- 


68 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig . 38 —Transformation of energy in a motor car 













































MAKING ELECTRICITY DO WORK 


69 


nected to a starting motor is not all transformed into mechanical 
energy, as a part of the output of the battery will be used in 
causing the electricity to flow through the resistance of the various 
parts of the circuit. This energy will manifest itself by heating 
the circuit; that is, it will appear as heat energy. All of the 
mechanical energy generated in the electric motor is not available 
to turn the engine crankshaft in starting as a part of the generated 
mechanical energy must be used in overcoming the friction of the 
bearing of the motor, the friction of the brushes on the commutator, 
the fan-like action of the armature as it revolves, which is called 
windage, and certain other losses which tend to prevent the arma¬ 
ture turning. 

Returning to the more important electrical circuits or circles of 
the motor car, we find the following transformations taking place 
as shown in Fig. 38. Mechanical energy is transformed into elec¬ 
trical energy in the generator and the magneto. Electrical energy 
is transformed into heat energy in the spark plug, the electric lamp, 
the electric heater, the cigar lighter, and in the various conductors 
carrying a current. Electrical energy is transformed into 
mechanical energy in the electric motor. Electrical energy is trans¬ 
formed into chemical energy in the storage battery when the battery 
is being charged, and the chemical energy in the battery is trans¬ 
formed into electrical energy when the battery is discharging. 

Electrical energy is transformed in magnetic energy in the induc¬ 
tion coil as it passes from the primary circuit into the magnetic 
field of the coil and this magnetic energy is transformed into elec¬ 
trical energy as the energy passes from the magnetic field into the 
secondary circuit. Electrical energy is transformed into magnetic 
energy and this magnetic energy into mechanical energy in the 
various solenoids with a movable armature or core as found in the 
cutouts, electric gearshifts, etc. 

It is desirable to have these various transformations take place 
as efficiently as possible. For example, a generator which gives 
out nearly as much electrical energy as it received mechanical energy 
is more desirable than a generator in which the output and input 
are widely different. Likewise, a battery whose electrical output 
after being charged is 80 per cent of its input on charge is a 
more desirable type, all other conditions being equal, than a battery 
whose output on discharge is 50 per cent of its input on charge. 


CHAPTER V 

Electrical Power 

P OWER is the rate of doing work, that is, it is the work done 
in a given time divided by the time. When the rate of doing 
work is 33,000 foot-pounds per minute the power is equal to 1 
horsepower. This rate of 33,000 foot-pounds per minute is the 
same as 550 foot-pounds per second, hence, if the rate of doing 
work is 550 foot-pounds per second, the power is equal to 1 horse¬ 
power. 

In the preceding chapter, we found that there was 5,000 foot¬ 
pounds of work done in raising 100 pounds of material from one 
floor of a building to another floor 50 feet above the first. The 
work done is independent of the time but the 'power required is 
dependent upon the time it takes to do the work. Thus, if it takes 
10 seconds for the hoisting machine to raise the 100 pounds 50 feet, 
the work done per second will be equal to 5,000 -j- 10, or 500 foot¬ 
pounds per second. Now, since 1 horsepower is 550 foot-pounds 
per second, the horsepower in this particular case will be equal to 
500 -r- 550 or 10/11 horsepower. 

The work done in raising the 1,200 gallons of water a vertical 
height of 100 feet was found to be equal to 1,000,000 foot-pounds. 
Now, if this operation is to be performed in 1 hour, the rate of 
doing work per minute will be equal to the total work done divided 
by the time in minutes, or 1,000,000 -5- 60, which is equal to 16,666.6 
foot-pounds per minute. The power the pump is developing in order 
to raise this quantity of water will be equal to 16,666.6 -r- 33,000, 
or .505 + horsepower. This is the power actually required to lift 
the water and does not take into account any power lost in the 
resistance of the pipe due to bends, ete. The power required to 
drive the pump will be greater than the power the pump develops, 
as part of the power is lost within the pump itself; hence, the horse¬ 
power of an electric motor which may be used in operating this 
pump must be quite a bit greater than .505 horsepower. 

Let us suppose that this quantity of Mater is to be raised in 2 
minutes instead of 1 hour, what horsepower will be required? Re- 


ELECTRICAL POWER 


71 


member the work done will be exactly the same but the power must 
be greater as the same work is to be done in a les 3 time in this case 
than in the previous case. The rate of doing work in this case is 
equal to 1,000,000 2, or 500,000 foot-pounds per minute. This 

rate of doing work divided by 33,000 gives the horsepower, which 
will be equal to 15.15 horsepower. It is obvious that the value of 
the horsepower required to perform a certain operation will increase 
as the time of doing the work decreases. 

The work done in raising a car weighing 5,000 pounds a vertical 
height of 50 feet we found to be equal to 250,000 foot-pounds. If 



Fig. 39 —Measuring power taken by a motor by means of an 
ammeter and a voltmeter 

this operation is to be performed in 2 minutes, the rate of doing 
work will be equal to 250,000 -5- 2, or 125,000 foot-pounds per minute. 
The horsepower required will be equal to 125,000 -s- 33,000, or 3.78 
horsepower. This is the horsepower actually required to raise the 
car and does not take into account any power required to take 
care of the friction of the elevating device. If the car were to be 
raised in 30 seconds or *4 minute, the rate of doing work would be 
equal to 125,000 -s- *4, or 250,000 foot-pounds per minute. The 
horsepower in this case then is equal to 250,000 -s- 33,000, or 7.57 
horsepower. 

The work aone in drawing the disabled car along the street, we 
found to be equal to 1,056,000 foot-pounds when the pull in the 
tow rope was 100 pounds and the car was pulled a distance of 2 
miles. Let us suppose this operation is performed in 15 minutes. 
The rate of doing work will be equal to 1,056,000 -r- 15, or 70,400 
foot-pounds per minute. The horsepower is equal to 70,400 -4- 33,- 
000, or 2.13 horsepower. 

Electrical power is the rate of doing electrical work, that is, it 
is the electrical work done in a given time divided by the time. 






















72 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

When the rate of doing electrical work is equal to 1 joule per second 
the power is equal to one watt. 

The work done in charging a certain storage battery we found 
to be equal to 100,800 joules. The time required to do this amount 
of work in this particular case was 1 hour, or 3,600 seconds; hence 
the rate of doing work was 100,800 -s- 3,600, or 28 watts. 

The work done in operating a certain starting motor we found to 
be equal to 126,000 joules. The time required to do this amount 
of work was 2 minutes or 120 seconds and the power is equal to 
126,000 -T- 120, or 1,050 watts. 

The power in any part of an electrical circuit may be determined 
by a more direct method than the one given above and this method 
may be developed as follows: In determining the work done we 
multiplied the current by the time in seconds in order to obtain 
the quantity of electricity passing through the circuit and this 
result was then multiplied by the value of the difference in electrical 
pressure or electrical level through which this quantity of elec¬ 
tricity moved. This result may all be condensed to the following 
simple statement: 

Electrical work in joules = current in amperes 
multiplied by time in seconds multiplied by 
difference in electrical pressure in volts 
joules = amperes X seconds X volts 

The electrical power is equal to the electrical work divided by the 
time in seconds required to do the work. Hence, if the above 
expression for electrical work be divided by the time in seconds, we 
have the value of the power equal to the current in amperes, times 
the difference in electrical pressure in volts, or 
Watts = amperes X volts 

The power required to charge the storage battery referred to above, 
then is equal to 4 X 7, or 28 watts. Likewise the power required 
to operate the motor is equal to 150 X 7, or 1,050 watts. 

Measurement of Electrical Power 

The power in an electrical circuit or any part of the circuit at 
any instant is equal to the product of the current in the circuit 
and the electrical pressure acting on the entire circuit or the part 
of the circuit in which it is desired to determine the power. For 
example, the current taken by a motor may be determined by con¬ 
necting an ammeter in series with the motor as shown in Fig. 39, 


ELECTRICAL TOWER 73 

and the electrical pressure between the terminals of the motor 
may be determined by means of a voltmeter connected directly to 
the terminals. The product of the current, as indicated by the 
ammeter, and the pressure, as indicated by the voltmeter, will give 
the power taken by the motor. 

The above method of measuring power is known as the voltmeter- 
ammeter method and it gives the value of the power when the 
circuit is carrying a direct current but does not necessarily do so 



Fig. 40— Measuring power taken by a motor by means of a 

wattmeter 


when the circuit is carrying an alternating current as will be ex¬ 
plained in the section dealing with the “ Alternating-Current Cir¬ 
cuit. ’ ’ 

The power in a circuit carrying either direct or alternating cur¬ 
rent may be measured directly by means of an instrument called 
the wattmeter. The construction of this instrument is such that it 
combines the ammeter and voltmeter in one instrument and the 
indication of the power is direct without having to multiply current 
and voltage. The general scheme of connections of the watt¬ 
meter is shown in Fig. 40, in which the terminals Aj and A 2 cor¬ 
respond to the ammeter connections and the terminals V* and V 2 
correspond to the voltmeter connections. 

Relation Between Mechanical and Electrical Power 

The relation between the electrical power in watts and the me¬ 
chanical horsepower has been determined experimentally and the 
results show that there are 746 watts in 1 horsepower. For example, 
if a generator is delivering a current of 15 amperes at a pressure 
of 7 volts, the power in watts will be equal to the product of the 
current in amperes and the pressure in volts, or 

Power in watts = 15 X 7 = 105 watts 















74 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The power in horsepower will be equal to the power in watts - 4 - 746, 
or 

Horsepower = 105746 = .14 horsepower or about 1/7 

The maximum current that a certain storage battery can safely 
deliver is 70 amperes and when this current is being taken from 
the battery the pressure between its terminals is 7 volts. What is 
the power output of the battery in watts and horsepower? 

Power in watts = 70 X 75 = 525 
Horsepower = 525 4- 746 = .703 

A generator delivers a maximum current of 20 amperes at a 
pressure of 12 volts and it has an efficiency of 60 per cent for this 
particular load. What horsepower will be required to operate this 
generator ? 

The output of the generator = 20 X 12 = 240 watts. 

The statement that the generator has an efficiency of 60 per cent 
means that 60/100, or 3/5 of the power required to drive the genera¬ 
tor, is in turn delivered by the generator to the circuit in which 
it is connected. The power delivered by the generator, or 240 watts, 
represents 3/5 of the power required to operate the generator. One- 
fifth of the power required to operate the generator will be equal 
to 240 -4-3, or 80 watts, and five fifths, or the entire power required 
to operate the generator, will be equal to 5 X 80, or 400 watts. 
This power in watts divided by 746 gives the horsepower required 
to operate the generator, or 

Horsepower = 400 - 5 - 746 = .53 horsepower 

Since power is the rate of doing work, or the rate of the expendi¬ 
ture of energy, that is, it is equal to work done or the energy 
expended divided by the time, we can say that the energy is equal 
to the power multiplied by the time. There are a large number 
of different units for work or energy and some of the more common 
ones are as follows: 

1 horsepower acting for 1 hour is called a horsepower-hour 
1 watt acting for 1 second is called a watt-second 
1,000 watts, or 1 kilowatt, acting for 1 hour is called a kilowatt-hour. 

For example, if a generator requires 10 horsepower to operate it, 
what energy will be required to operate the generator for 5 hours. 
The energy in horsepower-hours will be equal to the product of the 
power in horsepower and the time in hours which is equal to 10 
times 5, or 50 horsepower-hours. 

If a starting motor takes a current of 100 amperes at a pressure 



ELECTRICAL POWER 75 

of 6 volts, what energy in kilowatt-hours will be required to operate 
the motor for 2 hours? The power will be equal to 

100 X 6 = 600 watts, 

and the energy will be equal to 600 X 2 = 1,200 watt-liours. 
One kilowatt-hour is equal to 1,000 watt-hours, so to change a 
given number of watt-hours to kilowatt-hours, divide by 1,000. 
Then 1,200 watt-hours is equal to 

1,200 -f- 1,000 = 1.2 kilowatt-hours. 


Fig. 41 —.Two typical forms of watt-hour meters 

Measurement of Electrical Energy 

The electrical energy required to operate motors, lamps, heaters, 
etc., may be determined by multiplying the power by the time, 
provided the power remains constant throughout the entire time. 
This method of determining the value of the energy cannot be 
used, however, when the power in the circuit is fluctuating in value 
as in the case of a motor which is driving a variable load, such as 
would be found in the ordinary machine shop or in an electric car. 
The energy in such a case can be determined by means of a watt- 
hour meter whose dial reading is proportional to the energy that 
passes through the circuit in which the meter is connected. Watt- 















76 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

hour meters are used by the electrical power companies in measur¬ 
ing energy supplied to their customers and the difference in the 
readings on the dials of these meters at certain intervals repre¬ 
sents the energy used during the period between the times when the 
meter dials were read. Watt-hour meters are of numerous forms 
but they all measure energy. Remember that you do not buy elec¬ 
trical power, but electrical energy, and you usually pay a certain 
amount per kilowatt-hour. 

Two typical forms of watt-hour meters are shown in Fig. 41. 

How to Determine the Cost of Charging Storage 
Batteries 

Let us assume that a 6-volt storage battery is to be charged at 
the rate of 5 amperes for 15 hours from a 115-volt circuit and that 
the average voltage of the battery during the charging operation is 
7.0 volts. What will it cost to charge the battery if you have to 
pay 10 cents a kilowatt-hour for energy? 



Fig. 42 —Showing method of placing lamps in series when charg¬ 
ing battery to regulate resistance 


It will be necessary to place a bank of lamps or other resistance 
in series with the battery, as shown in Fig. 42, in order to prevent 
an excessive current flowing. The pressure acting on the resistance 
placed in series with the battery will be equal to the difference 
between the total pressure and the average pressure of the battery 
which is equal to 115 minus 7, or 108 volts. This pressure of 108 
volts is to produce the current of 5 amperes through the series 
resistance; hence, the value of the resistance will be equal to 
108 -T- 5 = 21.6 ohms. 


















ELECTRICAL POWER 77 

In charging the battery, a large part of the total energy drawn 
from the circuit will be transformed into heat energy in the charg¬ 
ing resistance and lost so far as the battery itself is concerned. 
The cost of all the energy drawn from the circuit, however, will 
have to be charged against the battery. The power in the charging 
circuit will be equal to 115 X 5 = 575 watts. 

The energy input to the battery circuit during the 15 hours will 
be equal to the product of the power in watts and’ the time in hours 
which is equal to 575 X 15, or 8,625 watt-hours. 

Dividing the value of the energy in watt-hours by 1,000 gives 
8.625 kilowatt-hours. 

The cost of the energy will be equal to 8.625 X $.10 = $.86. It 
is readily seen that the cost of charging a battery in the manner 
indicated above is almost prohibitive and it is due to the simple 
fact that such a large part of the total energy drawn from the 
charging circuit is used in the series resistance that had to be 
inserted in the circuit. Methods of calculating the number and 
arrangement of lamp to use as resistance for battery charging will 
be given later. 

If a number of batteries be connected in series and all be 
charged at the same time, the loss in the series resistance will be 
greatly reduced and the cost of the energy for each battery will 
be less than in the case of a single battery being charged alone. 

For example, suppose fifteen 6-volt batteries be connected in 
series and charged at a 5-ampere rate for 15 hours from a 115- 
volt circuit and that the average voltage of each battery during the 
charging operation is 7.0 volts. What will it cost per battery if 
you have to pay 10 cents per kilowatt-hour for energy? 

The total voltage over the fifteen batteries in series will be equal 
to 15 X 7 = 105 volts, 

and the pressure acting on the resistance placed in series with 
the battery will be equal to 115 — 105 — 10 volts. 

This pressure of 10 volts is to produce a current of 5 amperes, 
hence the value of the resistance of the series resistance will be 
equal to 10 -r- 5 = 2 ohms. 

The loss in this 2-ohm resistance will be less than 1/10 of the 
loss in the 21.6-ohm resistance, assuming they both carry the same 

current. 

The total energy drawn from the circuit will be the same in this 
case as it was in the previous case, since the value of the current, 
the pressure and the time are each the same. The cost of the 


78 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

energy in this case, however, is not charged up to a single battery 
but to fifteen, which greatly reduces the cost of charging a single 
battery as compared to the case when a single battery was charged 
at a time. In this case the cost per battery will be equal to .86 
divided by 15, or .057 dollars, or 5.7 cents. 

Torque 


The torque of an engine, electric motor, etc., is the tendency 
for the shaft of the engine, electric motor, etc., to turn. For 
example, if a lever be clamped to the shaft of a motor and a 



Fig . 43 —One of the most simple forms of measuring the torque 
of a motor 


spring balance attached to the outer end of the lever, as indicated 
in Fig. 43, the torque may be measured by noting the pull in 
pounds on the spring balance and then multiplying this reading 
by the distance from the center of the shait of the motor to the 
point where the spring balance is attached. 

Suppose the conditions are such that the net reading of the 
spring balance is 10 pounds and that the length L in Fig. 43 is i 3 /^ 
foot. Then the torque is equal to 10 X!%, = 5 pound-feet. The 
unit in which torque is measured is called the pound-foot. 






ELECTRICAL POWER 



79 

The torque of a revolving shaft may "be measured by means of a 
device called the prony brake, Fig. 43 illustrating 0110 of the 
simplest forms, though it usually is made to fit a pulley or fly¬ 
wheel instead of the shaft itself. 

It is interesting to note that the torque is independent of the 
value of the length L for if this length be increased or decreased 
there will be a corresponding decrease or increase in the value of 


Fig. 44 and 45 —Measuring torque "by means of two spring bal¬ 
ances and also by two sets of weights 

the net scale reading, all other conditions remaining constant. Fo* 
example, if you were holding on to the end of the arm L you would 
have to exert a greater force with a short arm than with a long 
arm in order to prevent the arm turning around, but the product 
of the force and the length of the arm would remain constant so 
long as the turning effort of the shaft remained constant. 

Suppose the prony brake is replaced by a rope as shown in Fig. 
44 and that there is a spring balance attached to each end of the 






























80 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


rope. The torque in this case is equal to the product of the radius 
of the pulley in feet and the difference in the readings of the 
two spring balances. The rope may be placed over the top of the 
pulley and weights W i and W o used instead of the spring balances 
as shown in Fig. 45, and the torque in this case is equal to the 
product of the radius of the pulley in feet and the difference in the 
readings of the two weights and W g . 

In Figs. 44 and 45, there is a force acting at the surface of the 
pulley which is equal to the difference in the readings of the 
spring balances or the difference in the two weights in pounds. 
This force acts through a distance in 1 minute equal to the distance 
a point on the surface of the pulley travels in 1 minute. If the 
radius of the pulley in feet be represented by R then a point on the 
surface of the pulley will travel around the circumference; that is, 
2 x 3.1416L or 6.2832 x R feet in each revolution. Now if the 
number of revolutions per minute be represented by r.p.m., the 
distance the point on the surface of the pulley travels in 1 minute 
will be equal to 6.2832 x R X r.p.m. 

This distance, multiplied by the force, which we will represent 
by W, will give the work done in one minute, or 


work per minute—6.2832 x R X r.p.m. x W 
The work done per minute divided by 33,000 will give the horse¬ 
power, or 


horsepower = 


6.2832 X R X W X r.p.m. 
33,000 


In the above expression R X W represents the value of the torque, 
hence the equation for horsepower may be written as follows: 

6.2832 X T X r.p.m. 
horsepower =- 5 ^- 


in which T represents the torque in pound-feet and r.p.m. represents 
the revolutions per minute. 


Determining Torque Starting Motor Must Develop 

Since the value of the torque is independent of the lever arm, 
it makes no difference whether the torque be measured as indicated 
in Figs. 44 and 45 or by means of the prony brake. 

The torque required to turn a gasoline engine over at a given 
speed may be determined in the following manner: If a wire be 
wound around the flywheel with one end of the wire fastened to 




ELECTRICAL POWER 81 

the wheel and the outer or free end attached to a spring balance 
and a pull then produced on the ring of the balance ample to turn 
the engine over at the desired speed, the torque required will be 
equal to the pull in pounds on the wire multiplied by the radius 
of the pulley in feet. The arrangement of this test is shown in 
Fig. 46. 

The starting motor must be capable of producing the same force 
et the surface of its pulley or gear when connected as shown in 
Fig. 46 as is required at the surface of the flywheel to turn the 
engine over. The torque of the motor, howerver, will be much less 
than the torque required to drive the engine, because the radius 
of the pulley or gear on the motor is much less than the radius of 




Fig. 46 —Determining torque necessary to revolve engine at 
definite speed 


the flywheel. The speed of the motor will be as many times greater 
than the speed of the engine flywheel as the radius of the flywheel 
is times the radius of the pulley on the motor. Neglecting losses, 
the output of the motor in horsepower will be equal to the input to 
the engine in horsepower, because the product of the speed and the 
torque in the two cases will be the same. 











CHAPTER VI 


Primary Batteries 

Voltage Cell 

I F two pieces of unlike metals be immersed in a solution, which is 
capable of acting upon one of them more than upon the other, 
there will be an electrical pressure set up between them. This elec¬ 
trical pressure will produce a current of electricity between the two 
pieces of metal when they are connected by a wire which passes from 
one piece to the other outside the solution. Such a combination of 
plates and solution constitutes w r hat is called a voltaic cell as it was 
first discovered by an Italian physicist, Volta, and was named after 
him. It is, however, sometimes called a galvanic cell, after Galvani, 
who was Volta’s contemporary. 

Two pieces of metal, such as copper and zinc, immersed in a solu¬ 
tion called the electrolyte of dilute sulphuric acid, as shown in 
Fig. 47, forms a simple voltaic cell. This cell is capable of produc¬ 
ing a continuous flow of electricity through a wire whose ends are 
connected to the zinc and copper strips. When the electricity flows, 
the zinc is wasted away, its consumption furnishing the energy re¬ 
quired to drive the electricity through the circuit composed of the 
solution, the two plates and the outside electrical connection between 
the plates. The cell, for convenience, might be thought of as a 
chemical furnace in which the fuel is zinc. 

The strip of metal from which the electricity flows as it passes 
through the portion of the circuit outside the cell is called the 
positive pole or positive terminal of the cell; while the plate toward 
which the electricity flows in passing through the portion of the cir¬ 
cuit outside of the battery is called the negative pole or negative 
terminal of the battery. In the above case, the copper will be the 
positive terminal and the zinc will be the negative terminal. The 
positive and negative terminals of a cell are usually designated by 
the plus ( + ) and negative (—) signs, respectively. 


PRIMARY BATTERIES 


83 


Primary and Secondary Cells 

If a cell is capable of producing an electrical current in a circuit 
directly from the consumption in it of some substance, such as zinc, 
it is called a prjmary cell. If, however, a current of electricity must 
first be sent through the cell to bring it into such a condition that 
it is capable of producing a current it is called a secondary, or stor- 




Figs. Jf7 and Jf8—Simple voltaic cell made of copper, zinc and 
sulphuric acid. Fig. Jf8, at the right, shows the chemical action 
in the cell 


age cell. The fundamental distinction, then, between a primary and 
a secondary, or storage cell, is that, with the latter type the chemical 
changes are reversible, while with the former type this is not prac¬ 
tical, even when possible. 

Action of a Primary Cell 

The action taking place in the primary and secondary cells, when 
they are delivering a current, is practically the same but the action 
in the primary battery is perhaps a little easier followed and it will 
be given in detail. The cell shown in Fig. 48, which is composed of a 






































84 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

piece of zinc and a piece of copper immersed in a solution of dilute 
sulphic acid, is a good example of a primary cell. Cu is the chemical 
symbol for copper and Zn for zinc. Water is composed of two parts 
of hydrogen, whose chemical symbol is H, and one part of oxygen, 
whose chemical symbol is 0, and, accordingly, water is represented 
chemically by the symbol H 2 0. 

Sulphuric acid is composed of two parts of hydrogen; one part of 
sulphur, whose chemical symbol is S; and four parts of oxygen. Ac¬ 
cordingly it is represented chemically by the symbol H 2 S0 4 . 

The sulphuric acid acts chemically upon the zinc, the acid is 
broken up into two parts, H 2 and S0 4 . At the same time the chem¬ 
ical action is taking place in the cell, there is a certain amount of 
electrical activity present. In this particular case, the two parts of 
the acid, H 2 and S0 4 , are charged with positive and negative elec¬ 
tricity respectively when they are separated. The S0 4 part possesses 
a negative charge and hangs on to the zinc plate, giving to the zinc 
plate a negative charge and at the same time combining with a part 
of the zinc, Zn. 

You can think of the zinc which combines with the S0 4 part of 
the sulphuric acid as taking the place of the H 2 part of the acid and 
making a new compound called zinc sulphate and represented chem¬ 
ically by the symbol ZnS0 4 . This zinc sulphate is dissolved by the 
water in the cell just as sugar is dissolved when it is placed in 
water. The result of the action at the negative or zinc plate is a 
wasting aw j ay of the plate itself, the formation of zinc sulphate, and 
the production of a negative charge on the zinc plate. 

The Ho part of the acid possesses a positive charge and, instead 
of hanging on to the zinc plate, as in the case of the S0 4 part of the 
acid, it passes over to the copper plate where it gives up its positive 
charge and then rises to the surface of the liquid and goes off into 
the atmosphere. As a result of this action, the positive or copper 
plate becomes positively charged. 

The entire chemical action within the cell is represented by the 
diagram given in Fig. 48. The acid is broken up into two parts, H 2 
and S0 4 . The H 2 part has a positive charge of electricity and travels 
in the direction of the current, and the S0 4 has a negative charge of 
electricity and it passes in the opposite direction to the current. The 
fact that the charges of electricity on the two plates are of oppo¬ 
site sign causes a difference in electrical pressure to exist between the 
tw r o plates. This difference in electrical pressure will produce a cur¬ 
rent in a conductor connecting the two plates and the chemical ac- 


PRIMARY BATTERIES 


85 


tion within the cell will continue to go on. The energy of the chem¬ 
ical action within the cell is transformed into the electrical energy 
of the electricity flowing in the circuit. 

If there 'is no electrical connection between the copper and zinc 
plate, outside the cell, the chemical action will go on until the two 
plates are charged, and it then stops. 

The action of all primary cells is similar to the one just described. 
That is, the electrolyte is always broken up into two oppositely 
charged parts, and these two parts give up their charges to the two 
plates. The difference in electrical pressure between the two plates 
depends upon the kind of plates and the composition of the electro¬ 
lyte, and is independent of the size of the plates or the volume of the 
electrolyte. 

Polarization 

The hydrogen gas is likely to cling to the positive plate after it has 
given up its charge and form a layer of hydrogen gas over the sur¬ 
face of the plate. This accumulation of hydrogen gas on the positive 
plate is called polarization. The hydrogen gas is a very poor conduc¬ 
tor of electricity and, as a result, the resistance offered by the cell 
itself to the flow of electricity through it, which is called the in¬ 
ternal resistance of the cell, is increased and a larger part of the elec¬ 
trical pressure between the plates is used within the cell in order to 
force the electricity through the higher resistance. As a result, there 
is a decrease in the pressure available outside the cell to force the 
electricity through the outside circuit. 

There is an electrical pressure set up between the film of hydrogen 
gas and the copper plate whose direction is opposite the electrical 
pressure between the zinc plate and the copper plate and as a result 
the net electrical pressure of the cell is decreased. 

Depolarization 

In order that a cell may operate satisfactorily, it is desirable that 
the hydrogen gas be removed in some manner from the positive plate, 
and this process is called depolarization. There are various methods 
employed to depolarize a cell and these methods give rise to the vari¬ 
ous forms of primary cells. 

One of the most common methods is to introduce into the electro¬ 
lyte some chemical, called a depolarizer , which has an excess of 
oxygen in it. The excess oxygen in the depolarizer readily combines 
with the hydrogen on the positive plate and forms water, whose 
chemical symbol is ILO. 


86 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

If the action of the depolarizer is rapid, which results in the 
hydrogen gas being removed as fast as it tends to accumulate on the 
positive plate, there will be no decrease in the pressure between the 
two plates of the cell even though it be operated continuously. A cell 
of this kind is called a closed-circuit cell. 

If the action of the depolarizer is less rapid and there is a gradual 
accumulation of hydorgen on the positive plate regardless of the 
action of the depolarizer, there will be a decrease in the pressure be¬ 
tween the two plates of the cell when there is a current through the 
cell, and as a result the cell may be used only intermittently in order 
to allow the oxygen in the depolarizer time to clear the hydrogen 
from the surface of the positive plate. A cell of this kind is called 
an open-circuit cell. The ordinary dry cell is a good example of the 
open-circuit type of cell, and it is a well known fact that the volt¬ 
age of a dry cell will decrease when connected to a circuit continu¬ 
ously. 

If a closed-circuit cell be allowed to stand on open circuit, that 
is without there being any outside electrical connection between the 
plates, the depolarizer in the majority of cases ruins the cell by 
causing certain chemical changes in the electrolyte. It is essential 
that the different types of cells be used in the kind of a circuit for 
which they are intended, in order that the best results may be ob¬ 
tained from the cells. 

Local Action 

In addition to the polarization action which takes place at the 
positive plate, there is an action taking place in the cell, usually at 
the negative plate, called local action. This local action is generally 
caused by some impurity in the material forming the plate. For ex¬ 
ample, suppose there is a small piece of carbon imbedded in the sur¬ 
face of the zinc but in contact with the electrolyte of dilute sul; 
phuric acid. It is readily seen that a small voltaic cell is formed 
when the piece of impure zinc alone is placed in the electrolyte as 
there are two different materials immersed in a solution which acts 
on one of them more than it does on the other. The acid will be 
broken up into two parts, H 2 and S0 4 , with positive and negative 
charges respectively. The S0 4 will cling to the zinc and give up its 
negative charge, and a part of the zinc will combine with the S0 4 
to form zinc sulphate, ZnS0 4 . The hydrogen goes to the piece of 
carbon and charges it positively, instead of going over to a second 
or positive plate. As a result of the presence of the impurity in the 


PRIMARY BATTERIES 87 

zinc a small cell is formed and the zinc is consumed but there is not 
terminal voltage as the carbon and zinc are in direct contact with 
each other and a short circuit is formed. 

Electrochemical Equivalent 

The rate at which the negative plate of a voltaic cell is consumed 
depends upon how much current is passing through the battery. If 
the plate is pure, there will be no chemical action when there is no 
current through the cell and hence no metal will be consumed. The 
rate at which the negative plate is consumed depends upon how much 
chemical energy must be converted into electrical energy in a given 
time just as the rate at which coal is consumed in the fire under a 
boiler depends upon how much heat energy must be transformed into 
mechanical energy and delivered by the engine. If the cell supplies 
1 ampere for 1 hour, there is a definite quantity of zinc consumed, and 
if it supplies 2 amperes for 1 hour, there is just twice the quantity 
of zinc consumed. If a current of electricity be sent through a cell 
in the opposite direction to that in which is tends to flow due to the 
pressure of the cell itself, there will be a reversed chemical action 
taking place in the cell and the same amount of zinc will be recovered 
from the electrolyte and deposited upon the zinc plate in 1 hour by 
a given current as was consumed in supplying the same value of cur¬ 
rent for 1 hour. The rate at which the zinc may be recovered from 
the electrolyte and deposited on the zinc plate will be twice as great 
for a current of 2 amperes as for a current of 1 ampere ; three times 
as great for a current of 3 amperes as for a current of 1 ampere; 
etc. This last operation of breaking up the electrolyte and depositing 
the metal contained in the electrolyte is called electrolysis. This is 
the principle used in electroplating. 

The quantity of any metal forming the negative plate of a cell 
which is consumed in 1 hour, when the cell is supplying a current of 
1 ampere, or which is deposited in 1 hour when a current of 1 ampere 
is caused to flow backward through the cell, is called the electro¬ 
chemical equivalent of the substance. 

Damage Due to Electrolysis 

Under certain conditions, considerable damage may occur to some 
part of an electrical circuit due to electrolysis. For example, if two 
pieces of metal which form a part of an electrical circuit are making 
poor contact with each other and this contact is moist, there will be 
a chemical action taking place at the contact when there is a current 
in the circuit which results in the metal from which the electricity 


88 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 
flows being wasted away and carried across the contact and deposited 
on the other piece of metal. 

Polarity Indicator 

The positive and negative terminals of a direct-current circuit can 
be determined by dipping the terminals, at some distance apart, into 
a tumbler of water. The current in passing through the water de¬ 
composes it into oxygen and hydrogen, the oxygen going in the oppo¬ 
site direction to the current and the hydrogen in the same direction 


Fig. 49 —To tell the positive 
terminal from the negative ter¬ 
minal of a battery, connect a 
wire to each pole and dip the 
ends of the wire in a glass of 
water. The current decom¬ 
poses the water into hydrogen 
and oxygen, the hydrogen ap¬ 
pearing on the negative pole 
and the oxygen on the positive 
terminal. As there is more hy¬ 
drogen than oxygen in water, 
the terminal giving of most 
bubbles is the negative. 


as the current. The volume of the hydrogen gas resulting from the 
decomposition of the water will be approximately twice as great as 
the volume of the oxygen gas, and hence, there will be more bubbles 
collected on the negative terminal than on the positive terminal, as 
shown in Fig. 49. 

A solution of iodide of potassium, with a little starch added, is 
sometimes sealed in a short piece of glass tubing and terminals pro¬ 
vided at the ends by which contact can be made with the solution. 
When a current is produced in the solution, iodine is liberated at the 
positive terminal and turns the starch blue around this terminal. 

The Leclanche Cell 

The Leclanche cell is a good example of an open type of wet cell, 
and its operation will be given somewhat in detail as the operation of 
the dry cell described in the next section is practically the same. The 
first forms of this cell consisted of a carbon rod imbedded in a mix- 







89 


PRIMARY BATTERIES 


ture of manganese peroxide, and broken carbon, all contained in a 
porous cup. This cup was placed in an electrolyte of ammonium 
chloride commonly called sal ammoniac, and the negative terminal 
was formed from a piece of sheet zinc bent into cylindrical form and 
surrounding the porous cup. The construction of the cell is shown 
in Fig. 50. The manganese peroxide forms the depolarizer and the 



Figs. 50 and 51—Leclanche cell, a typical ivet cell, at left, and a 
common type of dry cell at right 


only object of the porous cup was to hold the mixture of manganese 
peroxide and broken carbon around the positive plate. 

In the more modern forms of this cell, the porous cup has been dis¬ 
pensed with and a mixture of carbon and manganese peroxide are 
moulded together with a suitable binder. 

Dry Cell 

The modern dry cell, so extensively used at the present time, may 
be looked upon as a slight modification of the Leclanche cell. The 
chief difference between them is that only enough water is added 












































90 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

to the material forming the electrolyte to moisten it and an absorbent 
layer of starch paste, blotting paper, or cloth which separates the 
positive and negative poles of the cell. The negative pole is a hol¬ 
low zinc cylinder closed at one end, which also serves as a container 
for the remainder of the cell. The absorbent layer used to separate 
the positive and negative poles is saturated with a solution of sal 
ammoniac and zinc chloride and placed next to the zinc on the in¬ 
side of the cylinder. The remaining space between the absorbent 
layer and the carbon rod is filled almost to the top with a moist 
mixture composed chiefly of manganese peroxide and granulated 
carbon. The manganese peroxide acts as the depolarizer. The re¬ 
maining space at the top of the cup is usually filled with a pitch 
composition which seals the cell. Terminals are provided at the 
upper end of the piece of carbon and also at the upper edge of the 
zinc cup. A vertical cross section of a modern dry cell is shown in 
Fig. 51. 

The internal resistance of a good dry cell when new should be less 
than .1 ohm but may increase to several times this value within 6 
months to 1 year even though the cell may not be in use. 

The electrical pressure produced within a dry cell, called its elec¬ 
tromotive force, should be in the neighborhood of 1.5 to 1.6 volts 
when the cell is quite new. The pressure between the terminals of 
the cell, called its terminal voltage, is equal to the electromotive force 
of the cell when there is no current through the cell. The terminal 
voltage drops when a current is supplied by the cell, due to the in¬ 
ternal resistance and polarization of the cell. In the majority of dry 
cells, the effect of the counter electromotive force due to polarization 
is greater than the effect of internal resistance and the average ter¬ 
minal voltage of the cell during its useful life is not much greater 
than 1 volt. 

About ninety per cent of the people using dry cells test them by 
measuring the current they will supply when the terminals of the 
cell are connected directly to the terminals of a low resistance amme¬ 
ter. This sort of a test does not take into account such factors as 
the temperature, the kind of service for which the cell is to be used, 
etc., and as a result is not altogether reliable. The same cell will 
produce a different current through ammeters of different resistances 
due to there being a different resistance in circuit in the two cases. 
The higher current being produced with the low-resistance ammeter 
and the smaller current with the high-resistance ammeter. The 


PRIMARY BATTERIES 91 

maximum wattage output can be obtained when the resistance outside 
of the cell is equal to the resistance inside of the cell. 

The effect of temperature on the current a cell will supply when con¬ 
nected directly to the terminals of an ammeter is quite pronounced. 
There is a change in the value of the current of about 1 ampere for 
each 10 degrees centigrade change in temperature for all tempera¬ 
tures ranging in value from 0 to about 90 degrees. 

A good dry cell should produce a current, when its terminals are 
connected directly to an ammeter, of from 16 to 25 amperes with an 
external resistance not exceeding .01 ohm. A cell producing a cur¬ 
rent much less than 16 amperes is more than likely composed of cheap 
materials or it has been made for a long time. If the cell produces 



minal of one cell joined to the positive plate of the next 

a current much in excess of 25 amperes it is likely to polarize rapidly 
and as a result its terminal voltage will decrease faster than one 
which produces a lower current. 

The ampere-hour capacity of a dry cell ranges in value from 5 to 
25 ampere-hours, when discharging continuously through a resistance 
of 15 ohms until the terminal voltage drops to .5 volt, depending 
upon the quality of materials used, the age of the cell, the tempera¬ 
ture of the cell, etc. The ampere-hour capacity of a dry cell is 
greater when it is called upon to produce a small current than when 
it is called upon to produce a relatively large current. Thus a cell 
producing a current in a circuit of 16 ohms will supply a larger num¬ 
ber of ampere-hours than it would if producing a current in a 4-ohm 
circuit. 

The ampere-hour capacity of a battery on intermittent service, 
such as in ignition, is entirely different from its ampere-hour capac- 

















92 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ity when producing a current continuously. The terminal voltage will 
decrease more rapidly at first when the cell is producing a current 
continuously than when it is producing a current intermittently, but, 
after the cell has been in service for some time, the terminal voltage 
of the cell producing the current intermittently will decrease faster 
than the terminal voltage of the cell producing the current con¬ 
tinuously. 

An Electric Battery 

If a number of cells be connected in series—the negative plate of 
one cell joined to the positive plate of the next cell, and so on—an 
electrical pressure will be produced between the positive plate at 
one end and the negative plate at the other end equal in value to the 
sum of the pressures produced by the different cells connected in 
series. Three dry cells are shown connected in series in Fig. 52. 

If a number of cells be connected in parallel—the negative plates 



Fig. 53—Three dry cells connected in parallel or multiple s the 
negative plates of all joined together and the positive plates of 
all joined 

of all the different cells connected together to form one terminal 
and the positive plates of all different cells connected together to 
form a second terminal—an electrical pressure will be produced be¬ 
tween the positive terminal and the negative terminal equal in value 
to the pressure produced by a single cell, provided the different cells 
are each producing the same pressure. Three cells are shown con¬ 
nected in parallel in Fig. 53. 

Any series, parallel, or a combination of series and parallel connec¬ 
tions of cells constitutes a battery. 




















PRIMARY BATTERIES 93 

It is customary in practice to represent a cell by means of two 
parallel lines, instead of drawing a picture of the cell each time you 
want to show it in a diagram. In Fig. 54, a battery of three cells 
is represented. The long line corresponds to the plus ( + ), or posi¬ 
tive, terminal, and the short line corresponds to the minus (—), or 
negative, terminal. 

Proper Combination of Cells for Best Results 

Suppose that a piece of apparatus having a resistance of 16 ohms 
is to be operated from dry cells and that the voltr.ge must not be 
less than 2 volts at any time. Two cells connected in series will 
produce the desired results until their terminal voltage drops to 
1 volt per cell. If, however, four cells be used and they be con¬ 
nected two in series and the two series groups in parallel, a much 
long / '^ life will be obtained from the cells than when only two cells 
are used. 

In the first case, the two cells are each carrying the total current, 


+ + + 




Fig. 5Jt—Usual way of repre¬ 
senting a battery in wiring dia¬ 
grams. The -f and — marks 
usually omitted 


while in the second ease, each cell is carrying only one-half of the 
total current as there are two groups of cells in parallel. In the sec¬ 
ond case, each group of cells might be thought of as discharging 
through a resistance of 32 ohms rather than 16 ohms and the life 
will be more than twice as great as the life of the two cells when 
used alone or discharging through a resistance of 16 ohms. 

When a number of cells are connected in parallel, they should all 
produce the same electrical pressure and have the same internal re¬ 
sistance. If the electrical pressure in one path of the parallel cir¬ 
cuit is greater than the electrical pressure in the other path or paths, 
then there will be a current through the path of higher pressure into 
the path or paths of lower pressure. The direction of this current in 
the path of higher pressure will correspond to the direction of the 
pressure in that path, while the current in the path or paths of lower 
pressure will be in the opposite direction to the pressure in the re¬ 
spective paths. This condition of affairs results in the cells in one 








94 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

path discharging into the cells in some other path or paths and there 
is a chemical action taking place, which is detrimental to the life 
of the cells, even though there be no current supplied to the device 
or apparatus the cells are to operate. For this reason it is always 
advisable to have the total pressure in each path of a parallel circuit, 
formed by connecting a number of cells, the same. 

If the resistance of one path of a parallel circuit, formed by con¬ 
necting a number of cells in parallel, is greater than the resistance of 
the other path or paths, then a greater pressure will be required to 
produce a current of a certain value in this circuit than will be re¬ 
quired to produce a current of exactly the same value in the other 
circuits. The same loss or drop in pressure will be produced by a 
small current in the path of high resistance and by a larger cur¬ 
rent in the path of lower resistance. Assuming the total pressures 
in the different paths are equal, and since the pressure between the 
terminals of all the paths will be the same, then the drop or loss in 
pressure in each path will be the same, and hence, it is obvious that 
the current in each path cannot be of the same value. The path 
of higher resistance will carry a smaller current than the path or 
paths of lower resistance. In order that cells may operate satisfac¬ 
torily in parallel, it is desirable that the total internal resistance and 
the resistance of the connecting leads be the same in each path. 


CHAPTER VII 


Storage Batteries 


Distinction Between Primary and Storage Batteries 

W/HEN the negative plate of a primary battery is nearly con- 
W gumed, it is customary to replace it with a new plate; or, in 
the case of the dry cell, to replace the entire cell by a new cell. 
If a current of electricity be sent thr; ugh the cell from an outside 
source in a direction opposite to the direction of the pressure pro¬ 
duced by the cell and the metal in the electrolyte deposited back 
on the negative plate, instead of replacing the plate or the entire 
cell, the cell is called a storage battery. When a current is passed 
through a storage cell in the direction of the pressure; that is, 
from the negative to the positive plate within the cell, the cell is 
said to be discharging; and, when a current is passing through 
the cell in the opposite direction to its pressure; that is, from the 
positive to the negative plate within the cell, the cell is said to 
be charging. 

The fundamental principles of the storage battery differ in no 
way from the primary cell; that is, any primary cell could be used 
as a storage cell and have its negative plate restored by sending 
a current through the cell in the opposite direction to its pressure, 
as is done in the commercial types of storage cells. The ordinary 
primary cell cannot have its negative plate restored economically 
and hence it is commercially more efficient either to replace the 
negative plate by a new one or to replace the entire cell when the 
negative plate has nearly wasted away. There are, however, some 
certain combinations of plates and electrolytes which may be used 
as a storage cell when especially constructed for the purpose. 

You must get this fact clearly fixed in your mind —a storage 
cell does not store electricity, but it stores chemical energy. 

During the process of charging electrical energy is transformed 
into chemical energy and stored within the cell; while, during the 


96 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

process of discharging, chemical energy is transformed back into 
electrical energy. Neither of these transformations is made with¬ 
out some loss which prevents as much energy being drawn from 
the cell when it is discharging as was put into it when it was 
charging. 

Types of Storage Cells 

Storage cells may be divided into two main groups, according 
to the kind of materials used in the construction of the plates. 
These- groups are lead storage cells and non-lead storage cells, and 
the construction and operation of the two types will be discussed 
somewhat at length in the following sections. A great deal more 
attention will be given to the lead storage battery on account of 
its characteristic at present being such as to make it much better 
suited to the requirements of the starting and lighting equipment. 

Lead Storage Cells 

In the construction of the lead storage cell, the cathode, or 
positive plate, is composed of lead peroxide, Pb0 2 ; the negative 
plate, or anode, is composed of pure spongy lead, Pb; and the elec¬ 
trolyte is sulphuric acid, H 2 SO 4 , diluted with water, H 2 0. 

Spongy lead and lead peroxide are rather poor conductors of 
electricity and their mechanical characteristics are such that they 
cannot be made into plates themselves and it is necessary that they 
be supported by frames of some material which is stronger and 
harder, and at the same time a better conductor of electricity. The 
material used for these frames must be one which is not acted upon 
by the acid, as otherwise there would be a local action between the 
spongy lead and the frame or between the lead peroxide and frame 
whenever they happened to be in contact. The material that is 
most generally used in constructing these frames, usually called 
grids, is an alloy of lead and antimony, which is mechanically 
stronger and stiffer than pure lead and it is not acted upon to any 
great extent by the sulphuric acid. 

The lead peroxide and spongy lead are usually spoken of as the 
active materials, in order to distinguish them from the grids. The 
combination of active material and framework is spoken of as a 
plate. It is a positive plate when it is a combination of lead 
peroxide and the framework, and negative plate when it is a com¬ 
bination of spongy lead and the framework. 


STORAGE BATTERIES 97 

General Types of Lead Cells 

There are two general methods of attaching the active material 
of a plate to the framework and these methods of constructing 
the plates give rise to two types of lead cells. These two types 
are known as the Plante and Faure. 

The Plante plate is made by taking a sheet of lead and preparing 
its surface so that a large area is exposed and then oxidizing this 
surface into lead peroxide by treating the plate chemically or by 
means of an electric current, thus forming the positive plates. 
The negative plates are formed by taking the peroxide plates and 
connecting them as the cathodes with lead sheets as the anodes, 
in a solution of diluted sulphuric acid, and passing a current from 
one plate to the other from an outside source. The hydrogen 
set free from the acid combines with the oxygen of the lead 
peroxide and reduces the lead peroxide to spongy lead. This 
process results in a thin layer of active material being formed 
on the surface of the plate which is quite porous and firmly 
attached to the grid. The area of the surface of the lead plates 
may be increased by cutting a large number of narrow grooves 
in their surface or by corrugating the plates. In one particular 
type of construction for stationary batteries the area of the plates 
is increased by forming buttons of narrow strips of corrugated 
pure lead ribbon and forcing them into circular openings in the 
framework. 

The Plante type of grid is usually used where weight and space 
are of no great importance and for this reason they are not used 
to any great extent in motor car work. 

In the Faure plate, the active material, instead of being formed 
by chemical action or by the action of an electric current, as in 
the case of the Plante plate, is formed by introducing a paste of 
active material, formed principally from compounds of lead mixed 
with a weak solution of sulphuric acid and water, into openings 
in the grid. The composition of this paste or active material 
as used by the different companies may be quite different and it 
is also quite different for different types of cells in order that the 
finished plate may be made compact, porous and at the same time 
not readily crumble away. This type of plate is usually spoken 
of as the pasted plate, and it is used chiefly where it is desired to 
obtain the greatest possible capacity with a minimum of weight 


98 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

and space occupied. This type of lead plate is used more than 
any other type in motor car work. 

Chemical Action Within a Storage Cell When 
Discharging 

In discharging a storage cell the electrolyte H 2 S0 4 is split up 
by the action of the electric current into hydrogen, H 2 , and 
sulphion, S0 4 . The hydrogen, which passes in the direction of the 
current, is liberated at the cathode and combines with some of the 
oxygen in the lead peroxide forming water, H 2 0, thus converting 
the lead peroxide into lead oxide, PbO. The lead oxide is supposed 
to combine immediately with a part of the electrolyte, 1I 2 S0 4 , 
forming lead sulphate, PbS0 4 , and water, H 2 0. Lead sulphate 
is also formed at the anode by the sulphion, S0 4 , combining with 
the spongy lead, Pb. The cell will continue to deliver current until 
the plates are entirely reduced to lead sulphate, when all action 
will cease, as there is but one kind of material in contact with the 
electrolyte and a cell requires two kinds. In practice, however, 
the practical limit of discharge is reached before the surfaces 
of both plates are reduced to the same material. 

The lead sulphate which is formed during the process of dis¬ 
charging is more bulky than the active materials themselves, and, 
as a result, there is an expansion in the surface of the plates of the 
cell. The lead sulphate has a higher electrical resistance than 
the active materials, which causes the internal resistance of the 
cell to increase as the discharge continues. There is also a decrease 
in the density of the electrolyte as the discharge continues on 
account of the absorption of the sulphion, S0 4 , by the active 
material. 

The chemical action taking place in a lead storage cell when it 
is discharging is shown diagrammatically in Fig. 55. The direction 
of the current within the cell is from the negative plate whose 
active material is spongy lead, Pb, toward the positive plate 
whose active material is lead peroxide, P0 2 . The sulphuric acid 
in contact with the negative plate is broken up into S0 4 and H 2 , 
and the positively charged hydrogen, H 2 , carries its charge over 
to the lead peroxide plate where it gives it up and combines with 
the oxygen of the lead peroxide forming water. The S0 4 part of 
the acid in contact with the negativq plate combines with the 
spongy lead and forms lead sulphate, PbS0 4 . The acid in contact 
with the positive plate is also broken up into S0 4 and H 2 , and 


STORAGE BATTERIES 99 


a part of the oxygen in the lead oxide combines with the hydrogen, 
H 2 , forming more water, H 2 0. The sulphion, S0 4 , instead of going 
over to the negative plate combines with the lead of the lead 
peroxide to form lead sulphate, PbS0 4 . 


MOTOR 




Figs. 55 and 56 —Chemical action in a storage cell during dis¬ 
charge, at left, and during charge, at right 


The chemical action may be written in the form of an equation 
as follows: 

Action at positive plate, cell discharging 

Pb0 2 plus H 2 plus H 2 S0 4 produces PbS0 4 plus H 2 0 
Lead peroxide plus hydrogen plus sulphuric acid produces 
lead sulphate plus water 
Action at negative plate, cell discharging 
Pb plus S0 4 produces PbS0 4 
Lead plus sulphion produces lead sulphate 
There are two things which are taking place when the cell is 
discharging. First, the acid is continually growing weaker and. 
























































































100 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

second, the active materials, lead peroxide and spongy lead, are 
being replaced by lead sulphate. This lead sulphate is more bulky 
than the active materials which it replaces and as a result the pores 
in the surface of the plates become more or less filled, which 
to a certain extent prevents the acid and active materials coming 
into contact with each other. 

Chemical Action When Charging 

In charging a storage cell, a chemical action takes place which 
is just the reverse of the chemical action taking place when the 
cell is discharging. The lead sulphate, PbS0 4 , on the positive 
plate is converted back into peroxide of lead, Pb0 2 ; while the lead 
sulphate on the negative plate is converted back into spongy lead. 
The density of the electrolyte increases, due to the fact that the 
S0 4 part of the lead sulphate combines with hydrogen and forms 
sulphuric acid. 

The chemical action taking place in a lead storage cell when it 
is being charged is shown diagrammatically in Pig. 56. The direc¬ 
tion of the current within the cell is from the positive toward the 
negative plate. Two parts of oxygen combine with the lead part 
of the lead sulphate in the positive plate and form lead peroxide, 
P0 2 . The SO 4 part of the lead sulphate on the positive plate 
combines with two parts of hydrogen and form sulphuric acid. 
Two parts of hydrogen combine with the SO 4 part of the lead 
sulphate on the negative plate and form sulphuric acid; while 
the lead part of the lead sulphate on the negative plate remains 
on the surface of the plate as the active material. 

The chemical action may be written in the form of an equation 
as follows: 

Action at positive plate, cell charging 

PbS0 4 plus H 2 0 plus O produces Pb0 2 plus H 2 S0 4 
Lead sulphate plus water plus oxygen produces lead peroxide 
plus sulphuric acid 

Action at negative plate, cell charging 
PbS0 4 plus H 2 produces Pb plus H 2 S0 4 

Lead sulphate plus hydrogen produces lead plus sulphuric 
acid 

The changes taking place in a lead storage cell when it is charg¬ 
ing result in the lead sulphate on the positive plate being replaced 
by lead peroxide, the lead sulphate on the negative plate being 
replaced by pure lead and the electrolyte becoming stronger. 


STORAGE BATTERIES 101 

Arrangement of Plates in a Lead Storage Cell 

Every storage cell contains two kinds of plates, positive and 
negative. In some very small cells there are only two plates, one 
positive and one negative. In the majority of cases, however, there 
are a number of both positive and negative plates, and they are 
arranged alternately with respect to each other. All of the posi¬ 
tive plates are connected to lead bars which form the positive 
terminal of the cell, and all of the negative plates are connected 
to lead bars which form the negative terminal. Since there is a 
greater chemical action taking place at the surface of the positive 
plate than is taking place at the surface of the negative plate, it 
is customary to arrange the plates so that there is a negative 



Figs. 57 and 58 —A group of plates for a storage cell, at left; 
a separator, center, and an element, consisting of a group of posi¬ 
tive plates, a group of negative plates and their separators, at right 


plate on both sides of each positive plate, which results in prac¬ 
tically the same action taking place on both sides of every positive 
plate. With this arrangement, there will be required one more 
negative plate in a cell than there are positive plates. 

The plates are prevented from coming into contact with each 
other by means of what are called separators, which are generally 
made from wood, treated to remove all acids and other injurious 
matter. Other materials are used in the construction of separators, 
the principal one of which is rubber, but not to anything like the 
extent that wood is used. In some makes of cells the plates are 
held apart by means of special mechanical devices. The separators 
are made quite thin and they are usually ribbed vertically on on© 















102 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

side. The ribbed side is placed next to the positive plate which 
readily permits the comparatively large amount of active material 
which is loosened from the surface of the plate during the operation 
of the cell to fall to the bottom of the cell. 

A complete set of positive or negative plates fastened to a bar 
or strap of lead is called a group, and it will be spoken of as a 
positive or negative group depending upon whether the plates 
are positive or negative. A group of plates is shown in Fig. 57. 

A combination of positive and a negative group of plates to¬ 
gether with the separators constitute what is called an element. 
A complete element for a starting and lighting battery is shown 
in Fig. 58. 

Containers for Lead Storage Cells 

The container for a storage cell is the vessel containing the elec¬ 
trolyte and into which the element of the cell is placed. The 
container should always be made from a material that is not acted 
upon by the electrolyte and its mechanical characteristics should 
be such that it will withstand the excessive vibration of the motor 
car and ordinary abuse in handling. Rubber is generally used in 
the construction of the container for storage cells to be used on 
motor cars as it readily meets the above requirements. 

The container is usually constructed with stiff ribs across the 
bottom and on the inside which serve to support the element and 
at the same time provide a space below the element into which 
any sediment or loose material resulting from the operation of the 
cell may accumulate. 

The containing case is usually provided with a suitable cover 
which is sealed into position after the element has been put in 
place by means of some kind of a pitch compound. Special means 
are employed by the different companies in making a tight seal 
around the top of the cell and terminals of the groups where they 
pass through the cover of the cell. 

Each cell must be provided with a suitable vent through which 
the gas formed during the operation of the cell may escape, and 
through which the electrolyte may be poured into the cell and 
electrolyte or distilled water added as may be required from time 
to time. 

The various cells forming the storage battery are arranged in a 
substantial wooden box thoroughly coated with an acid-proof 
paint and provided with suitable handles for carrying the battery 


STORAGE BATTERIES 103 

and also for anchoring it in position on the car. In the majority 
of cases a layer of sealing compound is placed over the entire 
number of cells after they are all in place in the containing case, 
while in some- makes the sealing of each individual cell is ample 
to prevent any seeping of the electrolyte out into the wooden box. 
When the sealing of each cell is entirely separate, it is possible 
to remove any one of the cells from the battery for inspection 
or repairs a great deal easier than it is where the entire battery 



Fig. 59 —A 12-volt storage battery, showing how the cells arc ar¬ 
ranged and the plates uiithin them 

is covered with a layer of sealing compound. The arrangement 
of the various parts of a complete storage battery is shown in 
Fig. 59, a part being cut away so as to show the interior. 

Electrolyte for Lead Storage Batteries 

The electrolyte for lead storage batteries consists of pure sul¬ 
phuric acid and water. Concentrated sulphuric acid is a heavy, 
oily liquid having a specific gravity of about 1,835. This acid is 
diluted with water until its gravity is in the neighborhood of 1,270 
to 1,300 for a fully charged battery, as the best results are obtained 
in the operation of the battery with acid of this gravity. 

By the term specific gravity is meant the relative weight of any 
substarce as compared to water. Pure water is taken as a standard 
and its specific gravity is taken as 1 usually written 1,000 and spoken 
of as ten hundred. Thus, if you were to weigh a certain volume of 
water and then weigh an exactly equal volume of some other material, 
the specific gravity of the material would be equal to weight of the 


104 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

volume of that material divided by the weight of the same volume 
of water. 

The specific gravity of a material is not constant but will change 
with a change in temperature. If the temperature of sulphuric 
acid is increased there will be an increase in the volume of the 
acid, and although there will be no change in the strength of the 
acid due to heating, the expansion will cause it to have a lower 
specific gravity at the higher temperature. The decrease in specific 
gravity is approximately equal to .001 for each 3 degrees Fahren¬ 
heit increase in temperature. For example, if the electrolyte 
in a battery has a specific gravity of 1,270 at 70 degrees Fahrenheit 
and the temperature of the electrolyte is increased to 73 degrees 
Fahrenheit, this increase in temperature will cause the electrolyte 
to expand and the gravity will decrease from 1,270 to 1.269. If the 



Fig. 60 —Proportions of water and sulphuric acid to use to make 
electrolyte of any desired specific gravity . The upper curve gives 
the parts "by volume, quarts or pints, and the lower one, the 
parts by weight, pounds or ounces 

temperature of the electrolyte had decreased instead of increasing, 
the electrolyte would have contracted in volume and the gravity 
would have increased. Owing to the fact that a change in the 
temperature of the electrolyte does not change the strength of the 
electrolyte but changes its specific gravity only, there should be a 
correction made in the gravity readings of 1 point for each 3 
degrees change in temperature. Just as a matter of convenience, 
70 degrees Fahrenheit is taken as a standard temperature. 










































STORAGE BATTERIES 


105 


The electrolyte may be prepared so that it will have any desired 
density by combining definite portions of water and acid either by 
weight or volume, as indicated in Fig. 60. The following precau* 
tions should always be observed in mixing the electrolyte: 

TJse a glass or earthenware vessel, under no conditions 
use a metal one. Always pour the acid into the water, never 
pour the water into the acid. Stir the liquid constantly, 
while mixing with a wooden paddle or glass tube and allow 
it to cool before talcing a reading of the specific gravity or 
before placing it in the cells. 



Fig. 61 —Hoiv to fill the battery 
and test the electrolyte. At the 
right is shown the hydrometer- 
syringe, which tests the specific 
gravity of the electrolyte and also 
can be used for adding water to 
the cells 



The specific gravity of the electrolyte may be determined by 
means of a device called a hydrometer. This consists of a closed 
glass tube with a small quantity of lead shot or other heavy 
material sealed in one end, which serves to keep the tube in an 











TEMPERATURE 


106 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

upright position when it is placed in the liquid, and provided with 
a suitable scale marked on the glass tube or on a piece of paper 
inside the tube. The depth to which the hydrometer sinks in the 
liquid, whose specific gravity is being determined, as indicated oij 
the scale of the instrument where the surface of the liquid is in 
contact with the tube, is a measure of the specific gravity of the 
liquid. The temperature of the electrolyte may be determined by 
means ot a thermometer and corrections made in the specific gravity 
as has been explained above. 

For convenience in using the hydrometer, it is usually placed 
inside of a larger glass tube provided with a rubber bulb at one 



Fig. 62 —Temperature at which electrolyte will freeze. "Note tha% 
up to a specific gravity of 1,300, the greater the specific gravity , 
the lower the freezing point 


end and a suitable nozzle or short piece of hose at the other. This 
combination is known as the hydrometer syringe, and is shown 
complete in Fig. 61. If the bulb be squeezed and the lower end 
inserted into the electrolyte through the vent opening of the cell, 
electrolyte will be drawn up into the large glass tube when the bulb 
is released. It will of course be necessary to draw up sufficient 
electrolyte to float the hydrometer. The specific gravity should 
be read at the surface of the electrolyte when the syringe is in a 
vertical position and there is no pressure on the bulb. 

Care should be exercised in returning the electrolyte to the cell 
to make sure that it is not drawn from one cell and returned to 
another, which would result in the electrolyte in one cell being 






























STORAGE BATTERIES 


107 

weakened as water eventually would be put in to replace the 
electrolyte, while in the cell to which the electrolyte was trans¬ 
ferred there would be an increase in specific gravity. 

The temperature at which sulphuric acid freezes depends upon 
the specific gravity. The relation between the temperature at 
which the electrolyte will freeze and its specific gravity is shown 
by means of a curve in Fig. 62. It is readily seen from an inspec¬ 
tion of this curve that there is little danger of the electrolyte 
freezing unless the battery is discharged, in which case the specific 
gravity will be relatively low. 

The specific gravity of the electrolyte in a cell will change when 


1300 


-12oo 


Fig. 63 —How the spe¬ 
cific gravity of a cell 
drops as it is dis¬ 
charged. Note that bat¬ 
tery men usually write 
specific gravity as 
though it were based on 
a standard of 1,000; felloe 
thus, full charge 1,300. jjy 
However, the gravity 


really is based 
standard of 1; 
full charge 1.300 


on a 
thus, 


t00 fo 


SPECIFIC GRAVITY VARIATION I 
-WITH PERCENT CAPACITYJN MTW_ 


8o Oo 4o 

PERCENT CECITY IN MTTERY 


Zo 


the cell is being charged and discharged, increasing while the cell 
is being charged and decreasing when the cell is being discharged. 
This change in the specific gravity of the electrolyte offers quite 
a reliable means of determining the condition of charge of the cell. 
Assuming the electrolyte has a specific gravity approximately 
1,300 when the cell is fully charged, the specific gravity will drop 
as indicated in Fig. 63 as the cell discharges. 

Ampere-Hour and Watt-Hour Capacity of a 
Storage Cell 

The normal ampere-hour capacity of a storage cell is equal to the 
quantity of electricity in ampere-hours that the cell will supply 
when it is discharged at such a constant current that the terminal 
voltage of the cell wilj fall to 1.7 volts, in 8 hours. For example, 
a cell is said to have an ampere-hour capacity of 60 ampere-hours, 
which means that the cell will supply a current of 7.5 amperes 
continuously for 8 hours at 70 degrees Fahrenheit without the 
terminal voltage decreasing below 1.7 volts. The ampere-hour 
















108 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

capacity of a battery formed of a number of cells connected in 
series will be the same as the ampere-hour capacity of a single 
cell, but the pressure producing the current will be equal to the 
pressure of a single cell multiplied by the number of cells. If the 
cells be connected in parallel, the ampere-hour capacity of the 
battery will be equal to the ampere-hour capacity of a single cell 
multiplied by the number of cells, but the pressure producing the 
current will be equal to the pressure of a single cell. The ampere- 
hour capacity of each cell depends upon the total area of the plates 
exposed to the action of the electrolyte. 

The watt-hour capacity of a storage cell is equal to the ampere- 
hour capacity multiplied by the average voltage during discharge. 
The watt-hour capacity of any number of cells connected in parallel 
or series will be equal to the watt-hour capacity of a single cell 
multiplied by the number of cells connected in circuit, assuming 
they are all identical. 

The capacity of a given storage cell is not constant but depends 
upon a number of conditions, such as the temperature of the cell, 
the rate at which the cell is discharged, the specific gravity of the 
electrolyte, the attention the cell has received and the kind of service 
to which it has been subjected. 

The higher the rate of discharge, the lower the ampere-hour and 
watt-hour capacities of the cell and the lower the rate of discharge, 
the higher the ampere-hour and watt-hour capacities of the cell. 

This decrease in capacity due to high rates of discharge is largely 
due to the fact that the electrolyte has not ample time to penetrate 
the pores of the active material and as a result, some of the active 
material is not available. If a cell be discharged at a high rate to 
the minimum voltage allowed for that rate, and then allowed to 
stand for some time, it will be capable of delivering an additional 
quantity. Thus, a storage battery may appear to be completely 
exhausted when it has been used in operating the starting motor 
for a considerable time and it will not even operate the lamps at a 
reasonable voltage, but if allowed to stand unused for some time, 
an additional capacity may be drawn from the battery at approxi¬ 
mately normal voltage. 

The capacity of a cell varies a great deal, due to a change in 
temperature. There is a very marked decrease in the ampere-hour 
capacity with a decrease in temperature. The battery acts as though 
it were numbed, due to the cold, and unable to make the same 
effort, that it does at normal temperature. The capacity of the 


STORAGE BATTERIES 109 

battery will return when its temperature is returned to normal. On 
account of this decrease in capacity, due to a decrease in tempera¬ 
ture, it is always advisable to keep the battery fully charged during 
the winter or cold months, in order that it be capable of delivering 
ample energy to meet the requirements. High temperatures are 
harmful to the life of a storage battery and should always be avoided 
where it is possible to do so. The high temperature in the cell is 
usually due to an abnormal condition and an inspection of the bat¬ 
tery and system in which it is connected should be made in order 
to locate the cause of the trouble. If the high temperature is allowed 
to continue it will distort the plate, permanently injure the wood 
separators, and more than likely soften the rubber jars and tops 
to such an extent that they may be seriously distorted. 


CHAPTER VIII 


Care of Storage Batteries 

I N order that a storage battery may give the best service it is 
possible for it to give, it is necessary that it receive a rea¬ 
sonable amount of care and attention rather than waiting until 
it is exhausted before the motorist knows there is such a thing 
as a battery on your car, or how to take care of it. If the 
following general rules are followed with reasonable care the 
operation of any good make of lead storage battery should be 
quite satisfactory. 

I—Add nothing but pure water or sulphuric acid electrolyte 
of the proper specific gravity to the cells. Under no condition 
try to operate your battery by adding a non-freezing solution 
of any kind. Water must be added frequently enough to keep 
the plates covered as they may be seriously damaged if allowed 
to be exposed for any length of time. It will be found necessary 
to add water, more frequently in warm weather than in cool or 
cold weather, and for this reason it is best to make it a rule to 
remove the vent plugs and add the water once a week. 

In freezing or very cold weather, the w T ater should be added 
just before the car is started in order that the water and 
electrolyte in the cell may become thoroughly mixed while the 
battery is charging. The water is lighter than the acid and 
would remain at the top of the cell and probably freeze, but 
if charged immediately, the bubbles of gas formed when the cell 
is charging will serve thoroughly to mix the water and the 
electrolyte. Be careful not to add too much water as the cell 
will boil over when it starts to gas and some of the electrolyte 
will be lost, and it should be replaced with new electrolyte 
rather than water in order that the specific gravity of the elec¬ 
trolyte in the cell may remain practically constant for a fully 
charged condition of the cell. 


CARE OF STORAGE BATTERIES 


111 


II—The specific gravity of the different cells should be de¬ 
termined at frequent and regular intervals in order to determine 
if the battery is being properly charged. These hydrometer 
readings should be taken before adding the water to the elec¬ 
trolyte. In some cases, the electrolyte may be so low in the cell 
that it is impossible to get enough electrolyte up into the hydro¬ 
meter syringe to float the hydrometer. Water must then be 
added and the cell charged for some time in order that the water 
and electrolyte may mix thoroughly before a hydrometer read¬ 
ing is taken. The condition of charge can be determined by 
reference to the curve given in Fig. 63, when the specific gravity 
of the electrolyte is known. If the specific gravity of any one 
of the cells in the battery is below 1,150, the cell is completely 
discharged or exhausted and should be removed from the car 
and given a special charge. In some cases it will be impossible 
to increase the specific gravity of the electrolyte regardless 
of the time of charge, which is an indication that there probably 
is a short circuit inside the cell and in such a case it needs the 
attention of an experienced battery man. 

It occasionally happens that the specific gravity of the elec¬ 
trolyte tests in the neighborhood of perhaps 1,200 although the 
battery appears to be almost completely discharged as determined 
by a voltmeter or dim lights. This condition is due to acid 
having been added to the various cells to replace evaporation 
instead of adding just pure water, and in addition there is 
probably some trouble within the cell, such as plates in partial 
contact, etc. The battery should be given a complete charge, 
that is it should be charged until the voltage and specific grav¬ 
ity of each cell shows no change in value for a period of several 
hours. At the end of this charge, take the specific gravity of 
each cell and if it is above 1,300 draw off some of the electrolyte 
and add pure water until the specific gravity of all the cells 
test the same, which should be somewhere between 1,270 and 
1,300. If the specific gravity of the electrolyte tests low, with¬ 
draw some of it from the cell by means of the hydrometer 
syringe and add electrolyte having a specific gravity of about 
1,300 until the gravity of the electrolyte in the cell has been 
raised to the desired value. Remember that the cell should be 
charged for a period after water or electrolyte is added in order 
that the electrolyte may be mixed thoroughly. 


112 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

III—Care should be exercised in keeping the outside of the 
battery clean. It should be wiped off occasionally, and the 
compartment in which it is placed examined for excessive cor¬ 
rosion due to acid from a leaky cell or perhaps from acid which 
has run out of the vent hole at the top of the cell. Be careful 
in cleaning the battery not to get any impurities into the various 
cells. The connections to the battery should be examined thor¬ 
oughly at regular intervals to see that they are not working 
loose or becoming corroded. A rag dampened with weak 
ammonia may be used to counteract the acid in cleaning about 
the battery. Hard vaseline may be used to prevent excessive 
corrosion at the terminals. 

Charging the Battery 

The best results are obtained in charging a storage battery at 
such a rate that it will be completely charged in about 8 hours. 
The battery companies usually specify the rate at which their 
different types and sizes of cells should be charged and that rate 
should be followed. This charge should continue until there 
is no increase in either the voltage of the cell, as indicated by 
a voltmeter, or the specific gravity of the electrolyte as indi¬ 
cated by the hydrometer for a period of perhaps 5 hours. The 
electrolyte in the various cells should be gassing, that is, bubbling 
freely, before the end of the charge. 

In some cases, the temperature of the cell may become quite 
high during charge and, in such cases, it is best either to reduce 
the rate of charge or to stop the charge entirely until the tem¬ 
perature is lowered to a safe value. Under no conditions should 
the temperatures of the cell be allowed to exceed 110 degrees 
Fahrenheit. 

If a battery is completely discharged, it may take 20 hours 
or more to completely recharge it at the normal rate. This 
time may be reduced where conditions demand that the battery 
be charged in a shorter time, by charging the battery at twice 
its normal rate during the first part of the charge and then 
{reducing this rate to normal value as soon as there are any 
indications of gassing. But it is not recommended as the proper 
method of procedure to follow in general. The temperature of 
the cells should be watched carefully and the rate reduced if 
the temperature rises to the neighborhood of 110 degrees 
Fahrenheit. 


CARE OF STORAGE BATTERIES 


118 

In some caffes the temperature may become excessive, although 
there is little cr no gassing in the cells and the specific gravity 
is low. This is an indication of trouble in the cell and it should 
be examined by a battery man. 

A storage battery must be charged by sending a direct cur¬ 
rent through it from the positive to the negative terminals. 
Under no conditions try to charge it by using an alternating 
current as this will ruin the battery. In some places alternating 
current only is available, and in such cases it will be necessary 
to convert the alternating current into direct current. There are 
a number of different ways of accomplishing this. An alternat¬ 
ing-current motor may be operated from the alternating-current 
circuit and used to drive a direct-current generator which will 
supply the proper kind of charging current to the battery. A 



FILAMENT LAMPS 

Fig. 65 —Connections for charging a storage "battery 
from a 110 -volt circuit 

device known as a rectifier may be used to change the alternating 
current into direct current. These rectifiers are in general of 
the mechanical, mercury vapor or electrolytic type. 

If a single 6-volt battery is to be charged from a 110-volt 
D. C. circuit, connections may be made as shown in Fig. 65. A 
resistance must be placed in series with the battery, in order to 
regulate the value of the current and a very convenient resist¬ 
ance is to use a number of 110-volt 32-candlepower carbon- 
filament incandescent lamps connected in parallel and the com¬ 
bination in turn connected in series with the battery as shown 
in the figure. Each of the 32-candlepower lamps will allow ap- 













114 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

proximately 1 ampere to pass through the battery, so if the 
charging rate in amperes is known the number of lamps required 
will be equal to this rate. When 16-candlepower carbon-fila¬ 
ment lamps are used instead of the 32-candlepower ones, twice 
as many lamps will be required, as each 16-candlepower carbon- 
filament lamp will allow approximately only y 2 ampere to pass 
through the battery. If high-efficiency lamps, such as tungsten, 
be used, more lamps will be required as the current rating of 
the high-efficiency lamps is less than the current rating of 
carbon-filament lamps. 

When a 220-volt circuit is available instead of a 110-volt 
circuit, two 110-volt lamps must be connected in series as shown 
in Fig. 66. When a 550-volt circuit is available, five lamps must 
be connected in series and a sufficient number of these series 



Fig. 66 —Connections for charging a storage battery 
from a 220-volt circuit 

combinations connected in parallel to give the desired charging 
current. 

Several batteries may be charged in series more efficiently 
than by charging each battery alone. If several batteries be 
connected in series in place of the single battery shown in Figs. 
65 and 66, less resistance will be required in order that the proper 
charging current may pass through the batteries. The reason for 
this is that with an increase in the number of batteries in series 
there is a decrease in the value of the effective pressure acting 
in the circuit, which is equal to the difference between the pres¬ 
sure between the terminals of the charging circuit and the com- 
















CARE OF STORAGE BATTERIES 


115 


bined pressure of all of the batteries, in series, and hence there 
must be a decrease in the value of the resistance of the circuit 
in order that the current may remain constant. There is a limit, 
however, to the number of batteries that may be charged in 
series and this limit is reached when the combined pressure of 
all the batteries in series at the end of charge and with the 
circuit closed is exactly equal to the pressure between the 
terminals of the charging circuit. Under these conditions there 
is no resistance required in the circuit and all of the energy 
drawn from the charging circuit is used within the batteries 
instead of part of this energy appearing as heat in the resistance. 

Care of Battery When Not in Service 

It may happen that the battery will be out of service for a 
considerable period, as when the car is put away during the 
winter months, and during this time it should not be allowed to 
stand without attention. If the battery is to be out of service 
for only 3 or 4 weeks, it should be filled with pure water and 
given a complete charge the last few days the car is in service 
by using the lamps and starting motor very sparingly. The 
specific gravity of the electrolyte should test between 1,270 and 
1,300. The batteries should be entirely disconnected from all 
circuits as any slight leak will in time completely discharge ifr 
It should be put in a room whose temperature is fairly uniform 
and, if possible, in the neighborhood of 70 degrees Fahrenheit. 

If the battery is to be out of service for several months, it is 
perhaps best to send it to a reliable battery station for storage 
where it will receive the necessary attention from time to time. 
In some cases, this is not possible and if such is the case you 
may proceed as follows: Give the battery a complete charge by 
operating the engine of your car at a speed corresponding to 
about 20 miles per hour for a sufficient time to cause the battery 
to become completely charged. If direct current is available, it 
will be best for you to remove the battery from the car and 
charge it as outlined in the previous section. From 6 to 8-week 
intervals during the out-of-service period, water should be added 
to the cells and the battery given what is known as a refreshing 
charge; that is, the charge should continue until all the cells 
have been gassing freely for perhaps 1 hour, and the battery 
may then be allowed to stand for another similar period without 
attention. In the event that it is not possible to give the bat- 


116 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

tery a refreshing charge every 6 weeks or 2 months, it may be 
allowed to stand for a period of perhaps 6 months without any 
real serious damage resulting, although it is best to give it the 
refreshing charge or send it to the battery station. 

No matter what procedure is followed, water should always 
be added and the battery fully charged before it is put back 
into service. If the battery has stood for 5 or 6 months, without 
being charged, it should be charged for 40 or 50 hours at one- 
half normal rate before being put back into service. 


Chapter IX 

Magnets and Magnetism 

T HE name magnet was given by the ancients to certain black 
stones found in various parts of the world, principally at Mag¬ 
nesia in Asia Minor, which possessed the property of attracting small 
pieces of iron and steel. Later, the Chinese discovered that if a piece 
of this black stone were freely suspended by a string it possessed the 
very remarkable property of pointing always in the same direction, 
nearly north and south; thence they called the stone te lodestone , 1 ’ 
or li leading stone” and used it in this manner to assist them in 
navigating their ships. The natural magnet, or lodestone, is an ore 
of iron, and is called magnetite. 

Artificial Magnet 

If a piece of iron, or, better still, a piece of hard steel, be rubbed 
with a lodestone, it will be found to possess the properties or char¬ 
acteristics of the natural magnet; that is, it will attract light pieces 
of iron; it will point approximately north and south if freely sus¬ 
pended by means of a piece of string; and it can be used to mag¬ 
netize other pieces of iron or steel. Magnets made in this manner 
are called artificial magnets. 

Strong artificial magnets, however, are not made by using the 
lodestone, as it is impossible to make them strong enough by this 
method, but by methods described in a following section on electro¬ 
magnetism. 

Poles of a Magnet 

Certain parts of a magnet possess the property of attracting iron 
and steel to a greater extent than do other parts, and these parts 
are called the poles of the magnet. The poles of a bar magnet are 
usually situated at or near the ends of the bar, as shown in Fig. 67, 
which shows a bar magnet that has been dipped into iron filings; 
the filings are attracted and adhere in tufts at the ends. 


118 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

North and South Poles 

When a magnet is supported on a sharp pivot or suspended by a 
light thread, it adjusts itself to such a position that it points nearly 
north and south. A small elongated magnet thus suspended is called 
a magnetic needle. If such a needle be turned from the position 
which it naturally takes and is free to swing, it will at once return, 
swinging to and fro until it settles down in its original position. 
This tendency of the magnetic needle to set itself approximately 
north and south is the foundation of the compass. 

The end of the needle which points approximately toward the 
north geographical pole is called the north pole, and is usually 
marked with the letter N; while the other end of the needle is called 
the south pole. 

The north pole of a magnet is often called the positive or plus 



Fig. 67 —When a magnet is dipped in iron filings , the filings will 
cling to the ends of the magnets, which are called poles 


( + ) pole, and the south pole is often called the negative or minus 
(—) pole. Since the north or positive pole turns toward the north, 
it is sometimes called the north-seeking pole, and the south or nega¬ 
tive pole is sometimes called the south-seeking pole. 

Magnetic Attraction and Repulsion 

If a pole of a magnet is brought near a magnetic needle, it is 
found to attract one pole of the needle and repel the other pole. 
The north pole of the magnet may be determined by observing the 
position it takes when suspended by a thread and it will be found 
that the north pole of the magnet always repels the north pole of the 
needle and always attracts the south pole of the needle. Similarly, 


MAGNETS AND MAGNETISM 


119 

it win be found that the south pole of the magnet always repels the 
south pole of the needle and always attracts the north pole of the 
needle. 

This action shows that there are two kinds of magnetic poles, and 
that poles of the same kind repel each other and poles of opposite 
kinds attract each other. The action between two like magnetic 
poles is shown in Fig. 68, and the action between two unlike mag¬ 
netic poles is shown in Fig. 69. 

Induced Magnetism 

If a bar of soft iron be used instead of a magnet, it will be 
found that either end of the bar of soft iron will attract either pole 
of the needle. If one end of the iron bar be thrust into a quantity 



of fine iron filings and withdrawn, only a very few of the filings will 
adhere to the end of the bar. If, however, one end of the bar be 
thrust in a quantity of filings and one pole of a permanent magnet 
be presented to the other end of the bar and the combination then 
withdrawn, a large number of the filings will adhere to the end of 
the soft iron bar, as shown in Fig. 70. Practically all of the filings 
will fall from the end of the soft iron bar if the permanent magnet' 
be removed from the other end. The action between the soft iron 
bar and the compass needle will increase with a decrease in the dis¬ 
tance between them. Similarly, the ability of the soft iron bar to 
hold the filings will increase as the distance between it and the pole 







120 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of the permanent magnet decreases. In either case, the bar of soft 
iron becomes magnetized due to the action of the compass needle or 
the permanent magnet, and two magnetic poles are produced on it. 
The end of the bar nearest the magnetic pole on the compass needle, 
or permanent magnet, will be of opposite sign, while the end of the 
bar farther away from the compass needle, or permanent magnet, is 
of the same sign as the pole on the compass needle, or permanent 
magnet. Magnetism produced in this manner is called induced 
magnetism. 

The magnetism induced in a piece of iron may induce magnetism 
in another piece, and this in another piece, and so on; and thus a 
magnet may be made to support similar pieces of iron end to end as 



shown in Fig. 71, each of which has become a magnet by induction. 
The magnetism of each sucessive piece is weaker than in the preced¬ 
ing piece. 


Forms of Magnets 

Magnets are made to assume many different forms, depending in 
a great measure upon their application. The two principal forms, 
however, are known as bar and horseshoe magnets, respectively. A 
bar magnet is shown in Fig. 67 and a common type of horseshoe 
magnet, as used in the construction of magnetos, is shown in Fig. 72. 

A material in which magnetism may be induced, and which is 
therefore attracted by a magnet, is called a magnetic material. Iron. 






1^1 


MAGNETS AND MAGNETISM 

in its various forms, such as wrought iron, cast iron and steel, is the 
best magnetic material known. There are a few other materials, such 
as cobalt, nickel and chromium, that are slightly magnetic but very 
much less than iron. All materials which are not quite strongly mag¬ 
netic are usually spoken of as non-magnetic materials, since they 
are nearly neutral as regards magnetism. Unfortunately there is no 
insulator for magnetism as there is for electricity. 

Demagnetization 

Continuous jarring of a magnet will tend to cause its magnetism 
to disappear, or to demagnetize it. If a magnet be heated to a tem¬ 
perature about red heat, it becomes demagnetized, and the iron 



Fig. 70 —A magnet will induce magnetism in 
an iron or steel bar and temporarily make a 
magnet of it as shoicn at the left 

Fig. 71 —The magnetism induced in a piece of 
iron may induce magnetism in another piece, 
and that in another, as shown at the right 


at the same time, loses its magnetic quality and does not regain it 
until it cools to a lower temperature. Since a magnet tends to lose 
its magnetism so readily, it is customary to furnish the horseshoe 
form with what is called a keeper. The keeper is a piece of iron 
which may be placed across the poles of the magnet, which makes 


















122 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

a complete magnetic circuit and thus tends to prevent the demagneti¬ 
zation of the magnet by jarring. 

Coercive Force 

Some materials are more readily magnetized and demagnetized 
than others. For example, it is well known that soft iron is very 
readily magnetized, but loses practically all of its magnetism if it 
is slightly jarred after it is removed from the influence of the mag¬ 
netizing force. Hard steel is usually more difficult to magnetize, 
but it, on the other hand, does not lose its magnetism so early as 


Fig. 72 —A horseshoe magnet such 
as is commonly used in the ordinary 
magneto for ignition. It is simply a 
tar magnet of inverted U shape 


soft iron. In general the harder the steel, the harder it is to mag¬ 
netize and the more strongly it retains its magnetism. The prop¬ 
erty of a magnetic material which opposes its demagnetization is 
called its coercive force, and it is desirable to have a material of 
high coercive force in making strong permanent magnets. 

Retentiveness 

When a magnet is magnetized as strongly as possible, it is said to 
be saturated , and if the magnetizing force producing the magnetism 
be removed, the magnet will immediately grow weaker and it will 
continue to get weaker for a considerable period until the magnetism 
finally becomes permanent in strength. Magnets which have lost 
the temporary magnetism due to saturation are called aged magnets 
and they should always be used where it is desired to have a con¬ 
stant magnetic effect. The ability of a magnetic material to retain 
its magnetism after being magnetized is called its retentiveness. 
















MAGNETS AND MAGNETISM 


123 


Molecular Theory of Magnetism 

There are quite a number of experimental facts which lead to the 
conclusion that magnetism has something to do with the molecules 
of the substance, since any disturbance of the molecules causes a 
change in the degree of magnetization. If a glass tube full of hard 
steel filings be magnetized, it will behave toward a compass needle 
or other magnet as though it were a solid bar magnet, but it will 



Fig. 73 —a magnet may be broken into any number of different 
pieces and there mill appear in each piece a north and a south 
pole 

lose practically all of its magnetism as soon as the filings are 
rearranged with respect to each other by giving the glass tube sev¬ 
eral good shakes. A magnet will lose its magnetism when heated. 
A magnet may be broken into any number of different pieces and 
there will appear at each break a north and south pole as shown in 
Fig. 73. The strength of any magnet will be greatly reduced by 
hammering, twisting, or bending it. 

A theory often used to explain the above facts is as follows: In 





























124 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

/^n unmagnetized bar it is assumed that the molecules are each a 
tiny magnet and' that these molecules, or magnets, are arranged in 
no definite way, except that the poles of the different magnets 
neutralize each other throughout the bar. The supposed arrange¬ 
ment of the molecules in an unmagnetized bar is shown in Fig. 74. 

When the unmagnetized bar is brought under the influence of a 
magnetizing force, the tiny magnets are turned, due to the action 
of the outside magnetizing force, so that their north poles tend to 
point in one general direction and their south poles tend’ to point in 
the opposite direction. The supposed arrangement of the molecules 
in a magnetized bar is shown in Fig. 75. The opposite poles neutral- 



Fig. 74 —Assumed arrangement of molecules of iron in an unmag¬ 
netized tar 







Fig. 75 —Rearrangement of molecules in an iron tar } assumed to 
take place upon magnetization. Each molecule tecomes a ting 
magnet and all have their north poles pointing approximately one 
way 


ize each other in the center of the bar but there will be a north pole 
found at one end and a south pole at the other. 

The ease with which any material may be magnetized as compared 
to some other material will depend upon what might be termed the 
molecular friction of the material. Thus, the molecules in a bar of 
steel offer a greater resistance to a change in their position than 
do the molecules in cast iron. Steel, as a result, is harder to mag¬ 
netize than cast iron, and it will also retain it's magnetism after once 
magnetized better than cast iron for the same reason. 

Magnetic Pole of Unit Strength 

Some unit of measure must be employed in order to be able to 
express the strength of a magnet, and for this reason we have what is 
called a unit magnetic pole. A magnetic pole is said to have a 
strength of 1 when it will repel a magnetic pole of equal strength 








126 


MAGNETS AND MAGNETISM 

and of the same kind with a force of 1 dyne when they are one 
centimeter apart. There are 2.54 centimeters in 1 inch, and 444,823 
dynes in 1 pound, so that the force between two unit poles is very 
small. In the above definition the magnetic poles are supposed to be 
concentrated at points. The force acting between two poles will 
increase with an increase in the value of the product of their re¬ 
spective strengths and decrease as the square of the distance between 
them. 

Magnetic Field 

Any open space in which there will be a magnetic force acting on 
a magnetic material, if it be introduced in the space, is called a 
magnetic field. Every magnetic field possesses two properties which 
must be known in order that a magnetic field may be described. 



N ' J 



Fig. 76 —Direction of magnetic field about a magnet cs indicated 
by a compass 

These two properties are the direction of the magnetic field and the 
strength of the magnetic field. 

The direction of a magnetic field is defined as being the direction 
in which a north magnetic pole would be urged if it were placed in 
the magnetic field. Since a north magnetic pole cannot be separated 
from its equal south pole, the direction of the magnetic field may be 
determined by observing the direction in which the north pole of a 
short compass needle will point when it is placed in the magnetic 
field at the point where the direction of the field is desired. For 
example, the direction of the magnetic field surrounding a bar mag¬ 
net may be determined as indicated in Fig. 76. The shaded end of 
the compass needle indicates the north pole of the needle. It will 
be observed that the direction of the field is out from the north pole 






126 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of the magnet at one end; it is parallel to the magnet at the center 
of the magnet and from the north toward the south pole; and 
toward the south pole of the magnet at the other end. 

The strength of a magnetic field at any point is defined as being 
equal to the force in dynes acting upon a unit magnetic pole placed 
at the point in question. A magnetic field has unit strength when 



Fig. 77— Lines of force pass from the north pole of one magnet f# 
the south pole of another , when N and 8 poles are adjacent 



Fig. 78 —Lines of force pass between If and 8 poles of each mag¬ 
net when N poles are together 

it exerts a force of one dyne on a unit magnetic pole. A force of one 
dyne is very small, as there are 444,823 dynes in 1 pound. A uni¬ 
form magnetic field is one whose strength at every point is the same. 

Lines of Force 

For convenience, a magnetic field is imagined as being a space 
more or less filled with imaginary lines called lines of force. The 
strength of the magnetic field may be represented by drawing the 
proper number of these lines of force per square centimeter, the 
area being taken perpendicular to the direction of the field; and th*' 




























MAGNETS AND MAGNETISM 127 

positive direction of the lines is taken to correspond to the direction 
of the magnetic field. 

These magnetic lines of force which are supposed to constitute a 
magnetic field are supposed to possess two properties. They always 



Fig. 79 —A piece of non-magneiic material does not change the 
effect of a magnet 



Fig. 80 —A piece of magnetic material prevents the lines of force 
from the magnet from spreading out 


tend to shorten themselves and they repel each other, which in a 
measure accounts for the attraction between unlike magnetic poles 
and a repulsion between like magnetic poles. Thus in Fig. 77 the 
lines of force pass from the north pole of one magnet across the in- 





















128 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

tervening space and enter the south pole of an adjacent magnet. 
Any tendency of these lines to shorten will result in a force tending 
to draw the poles together, and any force tending to separate the 
lines themselves will result in a force tending to draw the two poles 
together. The action between like poles is shown in Fig. 78. 

Magnetic Screen 

The effect of a magnet upon a compass needle may be varied by 
introducing a sheet of magnetic material between the two. The sheet 
of magnetic material acts as a magnetic screen and prevents the 
lines of force from the magnet spreading out to the extent they would 
if no screen were used. Introducing a non-magnetic material, such 
as glass, between the magnet and compass needle does not interfere 
with the action of the magnet on the compass needle. The effect of 
the magnetic and non-magnetic material is shown in Figs. 79 and 80. 


Chapter X 

Electromagnetism 

I F a compass needle be placed near a horizontal conductor in which 
there is a current of electricity, it will be acted upon by a mag¬ 
netic force which will tend to turn the needle from its approxi¬ 
mately north and south position. The position occupied by the 
compass needle when it comes to rest will change with a change 
in the value of the current in the conductor, and also with a 
change in the distance between the compass needle and the con¬ 
ductor. If the direction of the current in the conductor be reversed 
and adjusted to exactly the same value as before, the deflection 
of the compass needle will be changed, and it will be deflected in 
the opposite direction from its normal position to that before. 
These experimentally proven facts prove: 

First, there is a magnetic field surrounding a conductor in which 
there is a current of electricity. 

Second, the strength of the magnetic field produced by the cur¬ 
rent depends upon the value of the current. 

Third, the strength of the magnetic field produced by the current 
varies with the distance from the conductor. 

Fourth, there is a definite relation between the direction of the 
magnetic field produced by the current and the direction of the 
current producing the magnetic field. 

Magnetism produced in this manner by an electric current is 
called electromagnetism. 

Direction of Magnetic Field 

The direction of the magnetic field produced by a current of 
electricity may be determined in exactly the same manner as the 
direction of a magnetic field due to a permanent magnet, namely, 
by determining the direction in which the north pole of a compass 
needle will point when placed in the field at the point where the 
direction is desired. If a compass needle be placed beneath a wire, 


130 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

as shown in Fig. 81, and a current produced in the wire from left to 
right, as indicated by the long straight arrow above the wire, the 
compass needle will move in the direction indicated by the two 
curved arrows at the ends of the needle. If the compass needle 
be placed above the wire, it will be deflected in the opposite direc¬ 
tion. The general direction of the magnetic field on the under 
side of the wire is toward the surface of the paper and directly 
above the wire, the direction of the magnetic field is away from 
the surface of the paper. If the compass needle be pivoted on 
a horizontal axis parallel to the wire, instead of a vertical axis as 



Figs. 81 and 82 —Effect on compass needle of magnetic field about 
a icire which has a current in it 


in Fig. 81, its north pole will point around the conductor in the 
same direction as the hands of a clock as you look along the con¬ 
ductor in the direction of the current for all positions in which 
it is placed. The same results may be obtained by placing the 
conductor in a vertical position and turning the compass njeedle 
around the conductor, the compass needle being free to move in a 
horizontal plane instead of a vertical plane. If the current in the 
conductor is down, as shown in Fig. 82, the direction of the mag- 

























ELECTROMAGNETISM 131 

netic field about the conductor will be clockwise, as indicated by 
the small arrow heads on the dotted line. 

If iron filings be sprinkled upon a sheet of paper through which 
a conductor passes that is carrying a current, the iron filings will 
arrange themselves in more or less regular concentric lines, when 
the paper is gently jarred, as shown in Fig. 83. 

Determining the Direction of Magnetic Field 

There are a number of simple methods of remembering the rela¬ 
tion between the direction of a magnetic field and the direction 



iron filings 



Fig. 84 —The magnetic field is in the same direction as the 
hands of a clock when the direction of the current is away from 
the observer (+) and anti-clockwise when turned toward the ob¬ 
server (—] 

of the current producing it. A very simple rule, known as the 
“right-hand rule,” is as follows: Grasp the conductor with the 
right hand, the thumb being placed along the conductor and the 
fingers around the conductor, then the fingers will point in the 
direction of the magnetic field when the thumb points to the direc¬ 
tion of the current in the conductor. 




















1-2 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

If you look along a conductor in the direction of the current, 
the direction of the magnetic field surrounding the conductor, due 
to the current in the conductor, will be clockwise. Two methods of 
representing the direction of a magnetic field in relation to the 
direction of the current in the conductor producing the magnetic 
field are shown in Fig. 84. A cross-section of the conductor is 
shown in each case, and a current from the observer is indicated 
by a plus sign ( + ), while a current toward the observer is indi¬ 
cated by a minus sign (—). The field is indicated by the con- 



Fig. 85 —Effect on a compass needle of current through a loop 

of wire 

centric dotted circles, and it is clockwise—the same direction as 
the hands of a clock—when the current is away from the observer 
and counter-clockwise when the current is toward the observer. 

Another rule, known as the li right-hand screw-rule , 1 ’ is as fol¬ 
lows: Consider a right-handed screw which is being screwed into 
or out of a block. If a current is supposed to exist through the 
screw in the direction in which the screw moves through the block, 
then the direction of the magnetic field will correspond with the 
direction in which the screw turns. 

Solenoids 

If a conductor be bent into the form shown in Fig. 85 and a 
current sent through the conductor, the magnetic action on a com¬ 
pass needle placed in the position shown in the figure, due to a 
certain current in the conductor, will be greater than in the case 
of a straight conductor. This is due to the fact that the magnetic 
effect of both the upper and lower portions of the conductor tend 

















ELECTROMAGNETISM 


133 


to produce a deflection of the compass needle in the same direction. 
Hence, if the conductor be coiled about the needle, each additional 
turn will produce an additional force, tending to turn the compass 
needle from the normal position. The magnetic effect of any cur¬ 
rent can be greatly increased in this way. 

A cross-section through a single turn of wire carrying a current 
and the magnetic field surrounding the turn are shown in Fig. 86. 
The current is toward the observer in the left end of the section 
of wire and away from the observer in the right end of the wire, 



Fig . 86 —Lines of force about a turn of wire carry¬ 
ing a current 


which results in the direction of the magnetic field about the upper 
part being counter-clockwise and about the lower part, clockwise. It 
is obvious that the direction of the magnetic field between the end 
cross-sections of the wire is downward, and all the imaginary lines 
of force that are supposed to constitute the magnetic field due 
to the current in the turn of wire pass through the turn in the same 
direction. 

The magnetic field is stronger in the center of the turn than it 
is outside, which is indicated by a larger number of lines of force 
per unit of area, as shown in the figure. 

If the number of turns forming the coil be increased, the 
strength of the magnetic field inside the coil will be increased, 
since the majority of the lines of force that surround each turn 
seem to pass around the entire winding instead of passing around 






134 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the individual turns. A cross-section of a coil composed of a num¬ 
ber of turns is shown in Fig. 87. Such a coil is called a solenoid. 

Polarity of Solenoid 

Solenoids carrying current exhibit all the magnetic effects that are 
possessed by permanent magnets. They attract and repel magnets, 
pieces of wire and steel, other solenoids in which there is a current, 
etc. The magnetic lines pass through the solenoid from the south 
pole to the north pole, and outside the solenoid from the north pole 
to the south pole, just as in a permanent magnet. 

A simple rule by which the polarity of a solenoid may be deter- 



Fig. 87— Cross-section of a solenoid slioicing lines of force 


mined, if the direction of the current in the winding is known, is 
as follows: If you face one end of the solenoid and the current is 
around the winding in a clockwise direction, the end of the solenoid 
nearest you will be the south pole and the other end will be the 
north pole. If the direction of the current in the winding is 
counter-clockwise the end nearest you will be the north pole and 
the other end the south pole. 

Another simple rule for determining the polarity of a solenoid 
is as follows: Grasp the solenoid with the right hand, placing the 
fingers around it in the direction of the current; the thumb will 
then point in the direction of the north pole, as shown in Fig. 88. 









ELECTROMAGNETISM 


135 


Magnetomotive Force 

When a current of electricity is produced in the winding of a 
solenoid, it becomes magnetized and lines of force pass through 
the interior from the south to the north pole and return outside 
from the north to the south pole. The current produces a force 
which drives the lines of force, called magnetic -flux, through the 
paths which they take, called the magnetic circuit, just as the 
electromotive motive force in the electrical circuit causes the elec¬ 
tricity to flow through the electrical circuit. Magnetic flux is meas- 



Fig. 88 —Easy method of finding north and south poles of a 
solenoid. With fingers of right hand in direction of current, 
thumb points to north pole 


ured in a unit called the Maxwell, and one Maxwell simply means 
one line of force. This force, due to the electrical current, is called 
magnetomotive force, and it is usually abbreviated to M. M. F. 

The magnetomotive force of a solenoid is directly proportional 
to the product of the number of turns in the solenoid and the 
current in amperes the turns are carrying. If the number of turns 
in the winding of the solenoid is represented by the letter N and 
the current in the winding by the letter I, then the magnetomotive 
force will be greater or less as the product N X I is greater or 
less. The product of the current and turns is called the ampere- 
turns, and the same magnetomotive force is obtained with a current 









136 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of 500 amperes through 1 turn, 25 amperes through 20 turns, 1 
ampere through 500 turns, etc. In each of the above cases the 
magnetomotive force is 500 ampere-turns. 

In making magnetic calculations, magnetomotive force is usually 
measured in a unit called the Gilbert. If a magnetomotive force is 
expressed in ampere-turns, it may be expressed in gilberts by 
multiplying the ampere-turns by 1.2566. Thus the magnetomotive 
force of 2 amperes in the winding of a solenoid of 50 turns is 100 
ampere-turns or 125.66 gilberts. 

Reluctance 

The magnetomotive force acting on any magnetic circuit encoun¬ 
ters a certain opposition to the production of a magnetic flux, just 
as the electrical pressure encounters a certain opposition in the elec¬ 
trical circuit to the production of an electrical current. The 
opposition offered by the magnetic circuit is called its reluctance, 
and it is represented by the letter S. The reluctance of a magnetic 
circuit depends upon the material composing the magnetic circuit 
and upon the dimensions of the magnetic circuit. It varies directly 
as the length of the circuit, inversely as the area of the circuit, all 
other conditions remaining constant, and inversely as a property 
of the material called its permeability, which will be defined later, 
represented by the symbol m The unit in which reluctance is 
measured is called the oersted. 

Permeability 

The number of lines of force passing through each square centi¬ 
meter of cross sectional area of the solenoid when there is no mag¬ 
netic core in the solenoid is called the field strength. The unit in 
which the field strength is usually measured is the gauss, and it is 
equal to 1 line of force per square centimeter. Field strength is 
frequently expressed as so many gilberts per centimeter; that is, 
it is equal to the magnetomotive force acting on a magnetic circuit 
divided by the length of the circuit in centimeters. Field strength 
is represented by the letter H. Any one of the following equations 
may be used in determining the value of the field strength: 

total magnetic flux maxwells 

H =-— __ 

area in square centimeters square centimeters 
This equation holds true for a uniform magnetic field but not for a 
non-uniform magnetic field. 



ELECTROMAGNETISM 


137 


magnetomotive force gilberts 


H = 


length 


centimeters 


or 


1.2564 X ampere-turns 


H 


centimeters 


If the magnetomotive force of a solenoid having a non-magnetic 
core can be maintained constant and an iron core be introduced in 
place of the non-magnetic core, the magnetic flux through the 
solenoid will be greatly increased. 

The number of lines of force per square centimeter in the mag¬ 
netic material is called the induction density and it is usually rep¬ 
resented by the letter B. The permeability of a material may be 



Fig. 89 —Two reluctances in 
series 


Fig. 90 —Two reluctances in 
parallel 


thought of as the ability of the material to conduct magnetic flux 
as compared to air. In making up a good magnetic circuit, it is 
always desirable to have materials of high permeabilities, in order 
that the reluctance of the magnetic circuit may be low. 


Ohm’s Law for the Magnetic Circuit 


The magnetomotive force acting as a magnetic circuit, the 
reluctance of the circuit, and the magnetic flux produced are 
related to each other just as the electrical pressure in an electrical 
circuit, its resistance and the current produced are related to each 
Other. This relation may be expressed as follows: 








138 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


magnetomotive force 

Magnetic flux --— 

reluctance 

Reluctance in Series and Parallel 

A magnetic circuit may be composed of several reluctances con¬ 
nected in series or parallel or a combination of the two methods 
just as an electrical circuit may be composed of several resistances 
connected in series or parallel or a combination of the two methods. 

If an air gap be cut in an iron ring, as shown in Fig. 89, the 
magnetic circuit composed of the iron ring and air gap will con¬ 
stitute a magnetic circuit in which two reluctances are in series. 



Figs. 91, right, and 92, left—Magnetomotive forces and reluc¬ 
tances in series 

The total reluctance of such a circuit is equal to the sum of the 
reluctances of the different parts, just as the total resistance of a 
series electrical circuit is equal to the sum of the resistances of the 
different parts. 

If two iron rings be placed side by side and a winding placed 
about both of them, the two rings will constitute a magnetic circuit 
in which two reluctances are in parallel. The two rings and winding 
may be arranged as shown in Fig. 90, but the reluctances of the 
two rings are still in parallel. 

Magnetomotive forces in series and parallel magnetomotive forces 
may be connected in series and parallel just as electromotive forces 
may be connected in series and parallel. For example, the mag- 




















ELECTROMAGNETISM 


139 


netomotive force of winding A in Fig. 91 is acting on the same 
magnetic circuit as the magnetomotive force of winding B. If 
these two magnetomotive forces both tend to produce a magnetic 
flux around the iron ring in the same direction, the total magneto¬ 
motive force acting on the magnetic circuit will be equal to the 
sum of the two. If, however, the two magnetomotive forces tend 
to produce a magnetic flux around the iron ring in opposite direc¬ 
tions, the total or effective magnetomotive force acting on the 
magnetic circuit will be equal to the difference between the two 
magnetomotive forces. The direction of the effective magnetomotive 




Fig. 93 —Two magnetomotive Fig. 94 —Magnetic circuits of 

forces in series acting on tioo a four-pole generator 

reluctances in parallel 

forces will correspond to the direction of the larger of the two 
magnetomotive forces. 

The magnetic circuit shown in Fig. 92 is composed of a number 
of reluctances in series and two magnetomotive forces in series. 
Two magnetomotive forces are shown acting in series on two mag¬ 
netic circuits connected in parallel in Fig. 93. The magnetic circuits 
of a four-pole generator or motor are shown in Fig. 94. In Figs. 
87 to 94, inclusive, the dotted lines indicate the path of the lines 
of force. The magnetomotive force acting on each of the magnetic 
circuits in Fig. 94 is equal to the sum of the magnetomotive forces 
of the two coils wound around the circuit. Each coil is common 
to two magnetic circuits in Fig. 94 and only one-half as many 
ampere-turns are required in each coil with this arrangement as 







140 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

would be required if the coils were wound around the outside por¬ 
tion of the magnetic circuits and around a single circuit instead 
of two. 

Hysteresis 

If a piece of iron be magnetized and the magnetizing force then 
removed, the induction density does not return to zero value. A 
magnetizing force must then be applied in the opposite direction in 
order to demagnetize the iron. The induction density may be built 
up to the original maximum value but in the opposite direction 
by increasing the magnetizing force. This lag of the induction 
density behind the magnetizing force is called hysteresis. 

This hysteresis property of the iron is supposedly due to a molecu¬ 
lar friction in the iron, and it results in the iron heating when it is 
rapidly magnetized and demagnetized. Certain grades of iron show 
a less hysteresis property than others and the manufacturers of 
electrical equipment endeavor to use this kind of iron, all other 
conditions being equal, when the iron is subjected to a rapid mag¬ 
netization and demagnetization in the operation of the apparatus. 


CHAPTER XI 

Electromagnetic induction 

BOUT 1831, Michael Faraday discovered that an electrical 



pressure was produced in a wire that was moved in a mag¬ 
netic field, when the direction of the motion of the wire was such 
that it moved across the imaginary lines of force forming the 
magnetic field. If this wire be made a part of a closed electrical 
circuit, the electrical pressure produced in the wire will cause a 
current of electricity in the circuit. Electrical pressures produced 
in the above manner are called induced pressures or induced electro¬ 
motive forces, and an electrical current produced by an induced 
electromotive force is called an induced current , and the phenome¬ 
non is called electromagnetic induction. In this great discovery lies 
the fundamental principle of the operation of many forms of igni¬ 
tion, starting and lighting apparatus such as magnetos, electrical 
generators, induction coils, etc. 

Electromotive Force Induced in a Wire by a Magnet 

If a wire AB, Fig. 95, that is connected in series with a gal¬ 
vanometer—an exceedingly sensitive ammeter—be moved in the 
magnetic field of a magnet, the needle will be deflected from the 
zero position. This deflection of the galvanometer is due to a 
current in it's winding which is produced by the induced electro¬ 
motive force in the wire that is moved in the magnetic field. When 
the movement of the wire in the magnetic field ceases, the galvan¬ 
ometer will show no deflection, which indicates there is no current 
and hence no induced electromotive force. Hence, the wires must 
be actually cutting the lines of force that are supposed to form the 
magnetic field in order that there be an induced electromotive force 
produced in the wire. 

If the wire were moved to the left, as indicated by the arrow C, 
across the magnetic field and the deflection of the galvanometer 
happened to be to the left, it will be found upon moving the con¬ 
ductor to the right, as indicated by the arrow D, or in the direc¬ 
tion opposite to its motion in the first ease, that the galvanometer 
will be deflected in the opposite direction from its zero posi* 


142 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

tion. Since the direction in which the indicator of a galvan¬ 
ometer is deflected depends upon the direction of the current 
through its winding, it is very apparent that the direction of the 
current in the second case is opposite to what it was in the first 
case; and, since the current is due to the induced electromotive 
force in the wire, it must also be in the opposite direction. If the 
motion of the wire in the magnetic field is continuous right and 
left, between the ends of the magnet, there will be a current through 
the galvanometer first in one direction and then in the opposite di¬ 
rection and the moving part of the galvanometer will swing to the 
right and left of the zero position. The motion of the wire, how¬ 
ever, may be rapid enough so that’ the moving part of the galvan¬ 
ometer has not sufficient time to take its proper position with re¬ 
spect to the current in the circuit, and as a result it remains prac¬ 



tically at zero, the movement or deflection to the right or to the 
left being very small. 

The same results can be obtained when the magnet is turned 
over and the south pole is at the top and the north pole at the 
bottom, except that the deflection of the galvanometer due to a 
given direction of motion of the wire will be just the reverse of 
what it was with the magnet in the original position. This shows 
that there is some definite relation betwen the direction of motion 
of the conductor, the direction of the magnetic field and the direc¬ 
tion in which the induced pressure acts. 

If the wire were held stationary and the magnet moved, the same 
results would be obtained as though the wire were moved between 
the poles of the magnet with the magnet stationary. Hence, it’ is 








ELECTROMAGNETIC INDUCTION 143 

only necessary that there be a relative movement of the wire and the 
magnetic field; either may remain stationary. 

An electromagnet may be used instead of a permanent magnet 
and the same results will be obtained under the same conditions. 

If the wire be moved very slowly across the magnetic field, the 
galvanometer will be deflected to a smaller extent than it would be 
if the wire were moved faster across the magnetic field. This de¬ 
flection of the galvanometer depends upon the value of the current 
sent through it and since the deflection is smaller when the wire is 
moved slowly than it is when the wire is moved fast, it must follow 
that the induced pressure for a slow movement of the wire is less 
than it is for a fast movement, even though all the magnetic lines 
forming the magnetic field be cut in each case. The above experi¬ 
mentally determined results show that the value of the induced 
electromotive force in a wire, due to a relative movement of a wire 
and a magnetic field, depends upon the velocity of the wire. If a 
second wire be connected in series with the first, so that the induced 
electromotive forces act in the same direction, the resultant, or 
effective, electrical pressure is increased. This is equivalent to in¬ 
creasing the length of the wire in the magnetic field. 

The electrical pressure may be increased by placing a second 
magnet along the side of the first so that the like poles are adjacent. 
This second magnet increases the strength of the magnetic field and 
the wire cuts more lines of force when it is moved. 

If the wire be moved in a path parallel to the lines of force form¬ 
ing the magnetic field there will be no deflection of the galvan¬ 
ometer, which indicates there is no current in the circuit and hence 
no induced electrical pressure produced in a wire due to its move¬ 
ment with respect to a magnetic field. The path in which the wire 
moves must make some angle with the direction of the magnetic 
lines of force. The value of the induced pressure due to the move¬ 
ment of a wire and a magnetic field with respect to each other will 
increase as the angles between the direction of the lines of force, 
the axis of the wire and the path in which the wire moves increases, 
and it will be a maximum when the wire moves in a path perpendic¬ 
ular to itself and the magnetic field. 

There will be an induced pressure set up in the wire even though 
the circuit of which the wire forms a part be open. This induced 
pressure will exist between the terminals of the circuit where it is 
opened just the same as an electrical pressure exists between the 
terminals of a battery that is on open circuit. 


144 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The question arises: Is the magnet weakened when it is used In 
producing induced pressures in a wire and if not, what is the source 
of energy that causes the current to exist in the wire? The magnet 
is in no way weakened when it is used as described and the in¬ 
duced current' is produced by the expenditure of muscular energy in 
moving the wire, just as the expenditure of chemical energy in a 
cell produces an electrical current in a closed electrical curcuit in 
which the cell is concealed. 

When a wire with a current in it is located in a magnetic field 
there is a force acting on the wire which tends to cause the wire to 
move across the field. The direction of this force is just the 
opposite to the one that must be applied to the wire to cause it’ to 
move, so there will be an induced pressure set up in the wire which 
will produce the current. In other words, the induced pressure set 
up in a wire will always be in such a direction that the current 
produced by it will oppose the motion of the wire. 

Current Induced in a Coil by Moving a Magnet 

If a coil of wire be connected in series with a galvanometer as 
shown in Fig. 96, a deflection of the galvanometer indicator can be 
produced by thrusting the magnet in and out of the coil. The fact' 
that part of the galvanometer indicator is deflected when the mag¬ 
net is moved inside the coil is proof that there is a current pro¬ 
duced in the circuit and it must be due to an induced pressure. 
When the magnet is thrust into the coil, a deflection of the galvan¬ 
ometer indicator will be produced, say, to the right, and when the 
magnet is withdrawn the galvanometer indicator will move to the 
left. If the magnet be turned end for end, the deflections of the 
galvanometer indicator will be just the reverse. If the coil itself 
be turned end for end and the magnet placed in its original position 
the deflection of the galvanometer indicator produced by a move¬ 
ment of the magnet in or out of the coil will correspond in direction 
to those produced when the coil was in its original position and the 
magnet had been turned end for end. 

If the coil be moved on or off the magnet, the same results will 
be obtained as when the magnet was moved in or out of the coil, 
The value of the induced pressure in this case, as in the previous 
one when the wire was moved in the magnetic field, will depend 
upon the velocity with which the magnetic field and coil move with 
respect to each other. 


ELECTROMAGNETIC INDUCTION 


145 


If the number of turns of wire composing the coil be increased 
or decreased, there will be a corresponding increase or decrease in 
the value of the induced pressure in the winding of the coil due to 
a given movement of the coil and magnet with respect to each other. 
The induced pressure in the various turns of the coil will all act in the 
same direction, and the effective pressure is equal to the sum of the 
induced pressures in the various turns. The induced pressure in 
each of the turns will have the same value at any instant, provided 
each turn is cutting the same number of lines of force at that par¬ 
ticular instant. 

Value of the Induced Pressure 

From the discussion above, it is seen that the induced pressure 
in an electrical circuit depends upon the following things: 

(a) The velocity of the wire and the magnetic field with respect 
to each other. The greater the velocity, the greater the induced 
pressure, all other things remaining constant. 



(b) The strength of the magnetic field, that is the number of 
lines of force per square centimeter. The stronger the field, the 
greater the induced pressure, all other things remaining constant. 

(c) The angle the path in which the wire moves makes with the 
direction of the magnetic field. The nearer this path is to being 
at right angles with the direction of the magnetic field and the 
axis of the wire, the greater the induced pressure. 

(d) The length of the wire actually in the magnetic field. The 
more wire there is in the magnetic field, the greater the induced 
pressure, all other things remaining constant. 

All of the above facts can be condensed into the following simple 
statement: The value of the induced pressure in any electrical 
















14(j ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

circuit depends upon the rapidity with which the wire forming the 
circuit cuts magnetic lines of force; that is, it depends upon the 
number of lines of force cut per second by the wire. 

When the wire cuts one hundred million lines in each second dur¬ 
ing its movement with respect to the magnetic field, an electrical 
pressure of 1 volt will he induced in the wire. 

If the wire cuts line of force at the rate of two hundred million 
lines of force per second, the induced pressure will be 2 volts; and 
if the wire cuts six hundred million lines of force per second, there 
will be an induced pressure of 6 volts. If the circuit in which this 
induced pressure is produced be closed, there will be a current pro¬ 
duced equal in value to the induced pressure divided by the total 
resistance of the circuit. 



Example: A wire cuts across a magnetic field of 10,000,000 
lines of force 60 times per second. (The conductor always moves 
across the field in the same direction.) What is the value of the 
pressure induced in the wire? ' 

Solution: A wire cutting 10,000,000 lines of force 60 times per 
second is equivalent to a conductor cutting 60X10,000,000, or 600,* 
000,000 lines of force once per second. If a conductor cut's 600,- 
000,000 lines of force per second, the value of the induced pressure 
will be equal to 600,000,000 divided by 100,000,000 or 6 volts. 

Direction of Induced Pressure 

From the previous discussion, it is seen that the direction of the 
induced pressure depends upon the direction of the magnetic field 
and the direction in which the conductor is moved with respect to 


























ELECTROMAGNETIC INDUCTION 


147 


the magnetic field. If a metal rod be bent into the form shown by 
A B C D, Fig 97, and a second rod E F be placed across the ends 
of the first rod and the combination placed in a magnetic field as 
shown by the vertical arrows in the figure, there will be a current 
around the circuit thus formed when the conductor E F is moved to 
the right or to the left of the initial position. When the conductor 
E F is moved, it cuts some of the lines of force of the magnetic field 
and there is an induced pressure produced in it which in turn pro¬ 
duces the current. The direction of this current will be reversed 
when the direction of the motion of E F, or the diiection of the 
magnetic field is reversed. 

When the wire E F is moved to the right, the end F is positive 
and the other end E is negative, or the electrical pressure induced 
in the wire tends to send a current around the circuit from F 



Fig. 98 —The lines of force might he thought of 
as elastic hands that are pushed aside 
when the wire is moved, then break 
and join on the other side 

through B and C to E. The wire E F is the part of the circuit in 
which the pressure is generated and the electricity will flow from 
a point of low pressure to a point' of higher pressure just as in the 
case of the battery. 

Determining the Direction of Pressure 

A simple way of determining the direction of the induced 
pressure when the direction of motion of the wire and the mag¬ 
netic field are known is as follows: Suppose a wire A, Fig. 98, is 
moved toward the right, as indicated by the horizontal arrow B, in 
a magnetic field whose direction is downward, as shown by the small 
arrow heads at the bottom of the figure. The lines of force might 
















148 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

be thought of as elastic bands that are pushed aside when the wire 
is moved in the magnetic field, but finally break and join on the 
left side of the wire, leaving a line linked around the conductor as 
shown by the circles C and D. The direction of these lines of force 
about the conductor is clockwise and they correspond to lines pro¬ 
duced by a current toward the paper, or away from the observer. 
Hence, the direction of the induced electrical pressure is toward the 
paper. It must be remembered that the electricity travels up hill 
electrically in this part of the circuit just as in the case of a cell. 

One of the best rules for remembering the relation between the 
direction of the magnetic field, the direction in which the wire 
moves and the direction of the induced electrical pressure is known 
as Pleming’s Right-Hand Rule and it is as follows: Place the thumb 



INDUCED 

PKESSUflE 

Fig . 99 —The right-hand rule for finding the direction 
of induced electromotive force 

and first and second fingers of the right hand all at' right angles to 
each other. Now turn the hand into such a position that the thumb 
points in the direction of the motion of the wire and the first' finger 
points in the direction of the magnetic field, then the second, or 
middle, finger will point in the direction of the induced pressure. 
An illustration of the Right-Hand Rule is shown in Fig. 99. 





ELECTROMAGNETIC INDUCTION 


149 


Primary and Secondary Coils 

If a coil of wire S be connected in series with a galvanometer as 
shown in Fig. 100, and a second coil P that has the winding con* 
nected to a battery be moved into or out of the coil S, there will be 
a deflection of the galvanometer, just as though a permanent mag¬ 
net had been used instead of the coil P. The coil S, in which thw 
induced pressure is produced, is called the secondary and the coil 
P, in which the inducing current exists, is called the primary. 

There are a number of different ways of producing an induced 
pressure in the secondary coil besides moving the primary coil with 
respect to the secondary coil. Four of these methods are as follows: 



Fig. 100 —The coil 8, in which the induced pressure is produced, 
is the secondary, and the coil P, in which the inducing current 
exists, is the primary coil 


(Both coils are stationary and one surrounds the other or they are 
both wound on the same magnetic circuit.) 

(a) By making or breaking the primary circuit: Imagine two 
wires A B and C D, Fig. 101, that are parallel to each other and 
very near together but connected in two electrically independent' 
circuits. The wire A B is in series with the galvanometer G and 
constitutes the secondary circuit. The wire C D is in series with a 




























150 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

battery E and a switch K which may be used in opening and clos¬ 
ing the primary circuit. When the primary circuit is completed by 
closing the switch K there will be a current through the wire C D 
from C toward D. This circuit will produce a magnetic field about 
the wire C D and the lines of force of this magnetic field will cut 
the wire A B, which will result in an induced pressure being pro¬ 
duced in the wire A B and causing a current from A toward B. The 
direction of the induced pressure can be determined by means of the 
Right-Hand Rule. There will be an induced pressure produced in 
the wire A B for r period of time corresponding to the time required 
to establish the current in the primary. As soon as the current in 
the primary becomes steady there will be no movement of the mag- 



Fig. 101 —How current is produced in an induction coil 


netic field and the conductor A B with respect to each other. When 
the current in the wire C D is increasing in value, the magnetic field 
surrounding the wire is expanding and moving outward across the 
conductor A B. 

If, now, the primary circuit be broken, the magnetic field sur¬ 
rounding the wire C D will collapse and, as a result, the wire A B 
will cut the magnetic field again, but in the opposite direction to what 
it did when the current in the wire C D was being established. There 
will be a current produced in the secondary circuit that is practi¬ 
cally constant in duration, if the primary circuit is made and broken 
a sufficient number of times. The current produced in the second¬ 
ary circuit is called an alternating current because it alternates in 
direction, it being in one direction when the current in the primary 
is increasing in value and in the opposite direction when the current 
in the primary is decreasing in value. 

The wires forming the primary and secondary circuits are usu 
ally wound into coils, and they may be placed side by side or onf 















ELECTROMAGNETIC INDUCTION 


151 


outside the other. The pressure induced in the secondary due to a 
given change of current in the primary in a certain time can he 
greatly increased hy placing the two windings on an iron core. The 
magnetic lines that passes through the two windings, due to t'he cur¬ 
rent in the primary, is a great deal stronger when they are placed 
on the iron core than it is when an air core is used and, as a re¬ 
sult, a greater number of lines of force will cut the secondary wind¬ 
ing when the primary circuit is completed or broken. 

The induction coil consists of two windings, a primary and a sec¬ 
ondary placed upon an iron core with a suitable device connected 



Fig. 102 —How the induction coil is applied to the ignition of 
a motor car engine 


to the primary circuit for interrupting the primary current. The 
relation between the pressure acting on the primary winding and 
the induced pressure produced in the secondary winding is practi¬ 
cally the same as the relation between the number of turns of wire 
in the primary and secondary windings. 

This is the method used in the simplest battery and coil ignition 
system as illustrated in Fig. 102. The s£ark plug in Fig. 102 re¬ 
places the galvanometer in Fig. 101 and the interrupter, or circuit 
breaker, replaces the switch K. The interrupter simply is an auto¬ 
matic switch which rapidly opens and closes the circuit. The wire 
between A and G in Fig. 101 is replaced in the ignition system by 
the metal of the engine between the spark plug and the coil terminal 

as shown in Fig. 102. . . 

(b) Varying the strength of the current in the primary: This m 

reality is practically the same as the previous method except the 
primary circuit is not’ entirely opened. Any change in the value of 
the primary current will result in a change in the magnetic field 





























152 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

surrounding the primary winding and as this field expands or con* 
tracts, it will cut the wire composing the secondary circuit and as a 
result there will be an induced pressure set up in the secondary 
winding. The direction of this induced pressure will depend upon 
whether the field is expanding or contracting, which, in turn, de¬ 
pends upon the change of current in the primary winding—whether 
it be increasing or decreasing. 

(c) Reversing the current in the primary: If a switch were con¬ 
structed so that its operation would reverse the current in the pri¬ 
mary winding of an induction coil at regular intervals, there would 
be an induced pressure produced in the secondary winding due to a 
change in the strength of the magnetic field through the two wind¬ 
ings. This method is applied in practice in what is called the trans¬ 
former. The switch, however, is not used as the current in the pri¬ 
mary winding is an alternating current, a current that is reversing 
in direction at regular intervals. 

(d) Moving a portion of the magnetic circuit about which t'he 
windings are placed: The magnetic field produced by a given value 
of current in the primary winding of an induction coil will depend 
upon the kind of material composing the magnetic circuit, whether 
it is a material of low or high permeability. If the core upon which 
the windings are placed or a part of the magnetic circuit be moved 
so as to change the reluctance of the magnetic circuit, there will be 
a change in the number of lines of force through the windings and, 
as a result, there will be an induced electrical pressure produced in 
the windings. If the reluctance of the magnetic circuit be in¬ 
creased, there will be a decrease in the number of lines of force, and 
if the reluctance be decreased there will be an increase in the number 
of lines of force, all other things remaining unchanged. When the 
lines of force through the windings decrease, there will be an in¬ 
duced pressure set up in the windings in the opposite direction to 
that set up when the magnetic lines of force increase. This prin¬ 
ciple is employed in what are called the inductor types of magnetos. 

Mutual and Self Induction 

The reaction of two independent electrical circuits upon each 
other is called mutual induction. These circuits must be so placed 
with respect to each other that the magnetic field due to the current 
in either of them will produce an effect in the other. The induction 
coil, or ignition spark coil, is a fine example of the practical appli¬ 
cation of mutual induction. 


ELECTROMAGNETIC INDUCTION 


153 


If the value of the current in a wire be changed in any way there 
will be a change in the strength of the magnetic field surrounding 
the wire. This change in the strength of the magnetic field will 
produce an induced pressure in the wire in which the current is 
changing in value just as though the magnetic field were changed in 
strength by a current in an independent electrical circuit. This 
property of a circuit which results in an electrical pressure being 
produced in the circuit when there is a change in the value of the 
current in the circuit is called the self inductance of the circuit. 
When a coil carrying a current' has its circuit broken, there will be 
a spark formed at the break due to the induced pressure. The value 
of this induced pressure depends upon the form of the coil and the 
kind of material associated with the coil. A straight wire will have 
a small pressure induced in it when the circuit is broken, as the mag¬ 
netic field surrounding the wire is not very strong. If the wire be 
bent into a coil, the induced pressure will be greater than that for 
the straight wire, as very nearly all the magnetic lines of force pro¬ 
duced by each turn of the coil cut all the other turns of the coil 
and the total number of lines of force cut by the wire forming the 
coil is greatly increased. This induced pressure can be increased 
further by providing the coil with an iron core, which increases the 
magnetic lines caused by any given current in the winding. 

In make-and-break ignition, it is desirable to have a hot spark 
at the point where the circuit is broken inside the cylinder, and for 
this reason a coil having a rather high self inductance is usually 
connected in series, which results in a large arc or spark being 
formed when the circuit is broken. 

Unit of Inductance 

A circuit’ is said to have a self-inductance of 1 henry when there 
is an electrical pressure of 1 volt induced in the circuit due to a 
change in the value of the current in the circuit of 1 ampere in 1 
second. That is, if the current changes, say, from 2 to 3 amperes 
in 1 second and there is an induced pressure of 1 volt, the circuit 
is said to have a self inductance of 1 henry. 

The mutual inductance between two circuits is measured in the 
**»me unit as the self inductance of a single circuit. If the current 
in one circuit changes at the rate of 1 ampere per second and as a 
result of this change there is an induced pressure of 1 volt pro¬ 
duced in a second circuit, the two circuits are said to have a mutual 
inductance of 1 henry. 


CHAPTER XII 

Generators and Motors 

A DYNAMO is a machine for converting mechanical energy 
into electrical energy or electrical energy into mechanical 
energy by means of electromagnetic induction. The dynamo, when 
used to transform mechanical energy into electrical energy, is 
called a generator , and when it is used to transform electrical 
energy into mechanical energy, it is called a motor . Bear in mind 
that the generator does not create electricity, but simply imparts 
energy to it, just as energy is imparted to the electricty as it 
passes through the primary cell. 

The dynamo consists, fundamentally, of two parts—a magnetic 
field, which may be produced by permanent magnets or electro¬ 
magnets, and an armature, which consists of a loop of wire or a 
number of loops, usually wound or mounted on an iron core or 
frame and so arranged that there may be a relative movement of 
the magnetic lines of force forming the magnetic field and the 
loop of wire. The movement of the loop of wire and the magnetic 
lines of force with respect to each other results in there being an 
electrical pressure produced in the loop. 

Simple Alternator 

If a single loop of wire is revolved in the magnetic field of a 
permanent magnet as shown in Fig. 103, there will be an electrical 
pressure induced in the two sides of the loop. If the terminals 
of the loop be connected to two metal rings C and D upon which 
brushes rest, this induced electrical pressure will produce a cur¬ 
rent in a circuit, such as a lamp, when it is connected to the 
brushes. The direction of the induced electrical pressure in the 
two sides of the loop may be determined by a simple application 
of Fleming’s generator rule, as given in a previous installment. 
The motion of one side of the loop with respect to the magnetic 


GENERATORS AND MOTORS 


155 


field is just the reverse to the motion of the other side. As a 
result of this difference in motion of the two sides of the loop with 
respect to the magnetic field, the electrical pressure induced in a 
side of the loop will be from the observer, while that induced 



Fig. 103 —The principle of the generator. This is the simplest 
alternating-current generator, in which a loop of wire is revolved 
about an axis A B in a magnetic field represented by the arrows 
passing beticeen the poles N and S of a magnet. The induced cur¬ 
rent caused by the wire cutting the lines of force is taken off the 
collector rings C and D by brushes to ivhich the outside circuit is 
connected 

in the other side will be toward the observer. These electrical 
pressures are in series and since their directions are opposite with 
respect to the observer, they both tend to produce a current in 






















156 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the same direction around the loop. There will be no induced elec¬ 
trical pressure in the ends of the loop since they cut no lines 
of force. 

The electrical pressure induced in either side of the loop at any 
instant will depend upon the number of magnetic lines cut in 
one second, or the rate at which the lines are being cut. This 
rate of cutting of the magnetic lines will depend upon the length 
of the two sides of the loop in the magnetic field, the strength 



Fig. 104 —Curve shounng the variation of electrical pressure 
induced in a loop of wire when it is revolved in a magnetic field. 
This represents a complete revolution of the loop, and it will be 
seen that the pressure increases from zero to a maximum during 
the first quarter, decreases to zero during the second, then changes 
in direction. This causes the alternating of the current 

of the magnetic field and the number of revolutions per second. 
Assuming the strength of the magnetic field is uniform, that at 
is the same at every part of the field and it remains constant in 
value, and the loop revolves about its axis at a constant speed, 
then the induced pressure in the loop will change in value, due 
only to a change in the direction of motion of the two sides of 
the loop with respect to the magnetic field. 

Thus, when the loop is in the horizontal position, the direction 
of the field also being horizontal, the two sides of the loop will 
be moving in a path, just for an instant, perpendicular to the 
direction of the magnetic field, and the rapidity with which the 
two sides of the loop are cutting the lines of force is greatest, 










GENERATORS AND MOTORS 157 

hence the induced electrical pressure in the loop is a maximum for 
this position of the loop. The value of the induced electrical pres¬ 
sure for positions intermediate between those just given will depend 
upon how fast the sides of the loop are actually moving across 
the magnetic field. 

A curve may be drawn which will show graphically the re- 



\ 

\ 

Fig. 105 —Simplest direct-current generator—a single loop and a 
two-segment commutator 

lation between the induced electrical pressure in the loop and 
its position with respect to a plane perpendicular to the magnetic 
field. Draw a line A B, as in Fig. 104, and divide this line into, 
say, twelve equal parts; each part will then correspond to 30 de¬ 
grees movement of the coil or loop about its axis. Start with the 
coil in a plane perpendicular to the magnetic field, and let this cor¬ 
respond to the point A in the figure; the electrical pressure induced 
in the loop for any movement from this position should be meas- 





























158 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ured off to a convenient scale on a perpendicular line drawn 
through the point on A B, corresponding to the displacement of 
the loop. Thus, the electrical pressure will be a maximum when the 
loop has rotated through an angle of 90 degrees. It then decreases 
as the angle increases from 90 degrees to 180 degrees and becomes 
equal to zero when the loop has rotated through an angle of 180 
degrees. The direction of the movement of the two sides of the 
loop with respect to the magnetic field changes just as the coil 
passes the 180-degree position and, as a result, the direction of 



Fig. 106— Curve showing the variation in electrical pressure 
produced by a generator with a two-segment commutator. It will 
be seen that the portion of the curve below the line in Fig. 104 is 
now above the line , and the current is constant in direction. 

the induced electrical pressure changes. The numerical values 
of the reduced pressure for the second 180 degrees are identical 
to those for the first 180 degrees, but they act around the loop 
in the opposite direction and are said to be opposite in sign. The 
difference in the sign is represented in the curve by drawing the 
second part of the curve below the horizontal line. 

Such a curve represents the change in pressure of a simple 
alternating current generator. 

Simple Direct-Current Generator 

The electrical pressure induced in the loop of wire described in 
the previous section may be made to produce a direct current—one 
that is constant in direction—in the external circuit in the follow¬ 
ing way: Suppose the two continuous metallic rings be replaced 
by a single ring composed of two parts that are insulated from 
each other, the distance between the ends of the two parts com¬ 
posing the ring being small in comparison to the total circum¬ 
ference of the combined ring. If the two ends of the loop be con- 









159 


GENERATORS AND MOTORS 

uected to these two parts of the ring, which are called segments, 
and two brushes that are insulated from each other be so mounted 
with respect to each other that they rest upon the insulation 
between the segments when the induced electrical pressure in 
the loop is zero, the connection of the external circuit with respect 



\ 

Fig. 107 —A direct-current generator having two loops of wire 
and four segments in the commutator. This makes the pressure 
more even a-s indicated in Fig. 108. When one loop is cutting 
the fewest lines of force, the other is cutting the greatest number 

to the loop will be reversed at the same instant the direction 
of the induced electrical pressure in the loop changes. This results 
in the induced electrical pressure in the loop always tending to 
send a current through the external circuit in the same direction. 

The proper arrangement of loop, segments and brushes is shown 
diagrammatically in Fig. 105. Such a machine constitutes a simple 
direct-current generator, because it delivers a current to the ex¬ 
ternal circuit in one direction. The two-part ring constitutes a 


























160 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

simple commutator of two segments and its purpose, as pointed 
out, is to reverse the connection of the external circuit with re¬ 
spect to armature winding, or vice versa, so that the induced elec¬ 
trical pressure in the winding will send a direct current through 
the external circuit. A curve showing the variation in the elec¬ 
trical pressure between the two brushes on a two-segment com¬ 
mutator is shown in Fig 106. An electrical pressure such as that 
represented in Fig. 106 is called a pulsating electrical pressure, 



Fig. 108 —Curve showing the variation in electrical pressure be¬ 
tween the brushes of a direct-current generator having two loops 
of wire and four segments in the commutator. When the pressure 
in one loop is zero, the pressure in the other loop is greatest, so 
that the pressure is more nearly uniform than is the case with one 
loop only 

because it pulsates or changes from zero to a maximum and back 
to zero at regular intervals, but does not change in direction. 

Four-Segment Commutator 

If the armature of a direct-current generator were constructed 
with a single loop of wire composed of one or more turns, the 
current delivered by such a machine would pulsate in value the 
same as the induced electrical pressure, as shown in Fig. 106. The 
operation of such a machine would be very unsatisfactory in a 
great many cases, especially in charging storage batteries. Fortu¬ 
nately, the electrical pressure between the brushes of the machine 
can be made to remain more nearly constant in value in the follow¬ 
ing manner: 

Suppose two loops of wire are used instead of one and that the 
ring is split into four parts instead of two and the brushes placed 
diametrically opposite each other and in such a position that the 
insulation passes under them when the loops each make an angle 



GENERATORS AND MOTORS 


161 


of 45 degrees with the magnetic field. The arrangement of loops, 
segments and brushes is shown in Fig 107. The induced electrical 
pressure in the two loops passes through a series of values similar 
to those represented by the curve in Fig. 104, but the induced 
pressure in one is greatest when the induced pressure in the other 
loop is zero. When the brushes are in the position shown in Fig. 
107, the electrical pressure between the brushes does not drop to 
zero value for any position of the two loops, as the brushes are 
always in contact with segments which in turn are connected to 
the ends of a loop in which there is an induced electrical pressure. 
The two loops are alternately connected to the two brushes and 
each remains in circuit for one-fourth of a complete revolution 
each time. Each coil is connected and disconnected twice during 
each revolution. The pressure between the brushes for such an 
arrangement of coils, segments and brushes as that shown in 
Fig. 107 is shown by the shaded portion of the curves in Fig. 108. 

The induced electrical pressure can be made more nearly con¬ 
stant by using more loops and more segments and placing them 
in such a position with respect to the first ones that the induced 
electrical pressure in the loops does not reach a zen maximum 
value at the same time it does in the others, and connecting them 
in such a way that the induced electrical pressure in all of the 
loops acts in series, parallel or series-parallel practically all of 
the time. 


Simple Ring Armature 

The operation of the generator having two loops of wire and 
four segment's in the commutator, as shown in Fig. 107, is not 
altogether satisfactory, as each loop is connected to the external 
circuit only while the brushes are in contact with the segments of 
the commutator to which the terminals of the loop are connected. 
An armature winding of this type is called an open-circuit winding. 

A better form of winding for direct-current dynamos, called a 
closed-circuit winding , makes use of all of the loops of wire all of 
the time except when the two commutator segments to which a loop 
is connected are in contact with a brush or brushes of the same 
polarity. One of the simplest forms of closed-circuit winding is 
shown in Fig. 109, which consists of an iron ring with four coils 
wound about it and interconnected by means of four commutator 
segments as shown in the figure. For convenience in referring to 
these coils they are designated as A, B, C and D. The two coils 



K>2 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

A and C are short-circuited by the two brushes when they are in the 
position shown in the figure. An instant later, however, coil A is 
in series with coil B on the right' side and coil C is in series with 
coil D on the left side, and this connection remains until coils B 
and D are short-circuited by the brushes. An instant later, coil D 
is in series with coil A on the right side and coil B is in series with 
coil C on the left side. 

It' is apparent that the coils opposite each other are short-circuited 
by the brushes at the same time when they are symmetrically ar¬ 
ranged, as in this case, and as one coil leaves the right circuit 
and enters the left circuit at the lower brush, there is a coil leav- 

A 


Fig. 109 —A jour-coil ring armature with a four-segment commutator 

ing the left circuit' and entering the right circuit at the upper brush. 
With this arrangement of commutator segments and coils, all of the 
coils are in circuit with the external circuit all of the time, except 
when they are short-circuited by the brushes. If the position of the 
brushes on the commutator is such that the coils are moving parallel 
to the magnetic field when the coils are short-circuited, there will be 
no electrical pressure induced in the coils and, as a result, the elec¬ 
trical pressure between the brushes is not decreased by short-circuit¬ 
ing the coils. 

The electrical pressure in all of the coils on the right side of a 












GENERATORS AND MOTORS 


1(53 


vertical line through the brushes will be in the opposite direction to 
the electrical pressure in the coils on che leit side of the vertical 
line through the brushes. The electrical pressures in the coils on the 
right and left sides of the vertical line act’ oppositely to each other, 
just as the electrical pressures of two batteries connected in parallel 
act opposite with respect to each other, but they act in the same 
direction with respect to the external circuit. 

The movement of the coils across the magnetic field just before 
they are short-circuited is in the opposite direction to their move¬ 
ment across the magnetic field after they have been short-circuited. 
This results in the electrical pressure induced in the coils before 
they are short-circuited acting around the 3oil in the opposite direc- 



Fig. 110 —Curve showing variation of electrical pressure between 
the terminals of a four-coil ring armature tvith a four-segment 
commutator 


tion to that in which the electrical pressure induced in the coil 
after it has been short-circuited acts. In other words, the electrical 
pressure induced in the coil reverses in direction while the coil is 
short-circuited. 

The total electrical pressure between the brushes at any instant’ 
will be equal to the sum of the electrical pressures induced in the 
coils connected in series between the brushes. When the coils are 
symmetrically placed, as shown in Fig. 109, the variation in the 
electrical pressure between the brushes will correspond to the varia¬ 
tion in the total pressure of the coils connected in series between 
the brushes. Thus the electrical pressure induced in the coil A with 
respect to the external circuit may be represented by a curve similar 
to the one marked A in Fig. 110. Both parts of the curve are drawn 
above the horizontal line, as the connection of the coil with respect 
to the external circuit changes when the coil passes the position of 




1G4 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

short-circuit or the position where the induced electrical pressure 
reverses in direction. The electrical pressure induced in the coil D 
with respect to the external circuit may be represented by a second 
curve D. The electrical pressure in A is a maximum when the elec¬ 
trical pressure in D is zero and the electrical pressure in D is a 
maximum when the electrical pressure in A is zero. The electrical 
pressure between the brushes at' any instant will be equal to the sum 
of the pressures induced in the two coils connected in series at that 
instant, and it may be represented by a third curve whose height 
above the horizontal is equal to the sum of the height of the two 


Fig. Ill —A six-coil ring armature with a six-segment commutator 

curves A and D. This third curve is shown heavy. From an inspec¬ 
tion of Fig. 110, it is seen that there are four loops to the shaded 
curve and that the pressure fluctuates in value. By increasing the 
number of coils on the ring and the segments in the commutator, 
the number of fluctuations in the pressure between the brushes for 
one revolution will be increased and the variation in the pressure 
decreased. A six-coil armature and six-segment commutator are 
shown in Fig. 111. The electrical pressure between brushes for 
such a combination of coils is shown by the shaded curve in Fig. 










GENERATORS AND MOTORS 165 

112. The height’ of this shaded curve is equal to the sum of the 
heights of the three other curves. 

Multipolar Ring Armature 

The armature of a generator may be revolved in a magnetic field 
of more than two poles, providing the connections of the various 
coils and the position of the brushes are properly made. For ex¬ 
ample, a four-pole armature is shown in Fig. 113. Four brushes 
are used and alternate ones are of the same polarity and connected 
together. The brushes are shown inside the commutator; they are in 
reality, however, outside. In passing from the negative terminal 
of such a winding through the winding to the positive terminal there 
are four possible paths. If this were a six-pole armature there 



Fig. 112 —Curve showing variation in electrical pressure between 
the terminals of a six-coil ring armature with a six-segment com¬ 
mutator 


would be six paths and so on. There are types of windings, how¬ 
ever, in which the number of paths through the winding may be 
greater than the number of magnetic poles forming the magnetic 
circuit and in some the number of paths may be less than the number 
of poles. Space will not permit a discussion of these various types, 
and the reader should make use of a book devoted entirely to arma¬ 
ture windings if he cares to investigate the many possible types. 

Simple Drum Armature 

In the case of the ring armature, the wire forming the winding is 
wound on an iron ring, while in the drum armature the winding is 

















Fig. 113— A sixteen-coil ring armature operating in a four-pole 
magnetic field 

are on the surface of the armature and have an electrical pressure 
induced in them. 

That part of an armature winding in which the electrical pressure 
is induced is called an inductor and there will be as many inductors 
in a ring winding as there are turns, while in a drum winding there 
will be twice as many inductors as there are turns. 

Electrical Pressure Induced in Armature Winding 

The electrical pressure induced in an armature winding will depend 
upon the rapidity with which the magnetic lines of force are cut 


166 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

placed around a cylinder of iron. The drum armature has a decided 
advantage over the ring armature in that more of the wire used in 
the winding has an electrical pressure induced in it. In the ring 
winding the part of each turn of wire inside the ring has practically 
no electrical pressure induced in it, and as a result only the part of 
each turn on the outside of the ring is effective in producing an 
electrical pressure. In the drum winding, both sides of each turn 

















GENERATORS AND MOTORS 


1G7 


by the inductors composing the winding. The magnetic lines of force 
cut by each inductor in one revolution is equal to the product' of the 
number of magnetic poles forming the magnetic circuit and the 
magnetic lines of force entering or leaving the armature at each pole. 

The number of magnetic lines of force cut by each inductor in one 
second will be equal to the product of the lines cut per revolution 
and the number of revolutions per second. 

The electrical pressure induced by the armature winding will de¬ 
pend upon the manner in which the inductors forming the winding 
are connected, that' is, whether there are two circuits through the 
winding, four circuits, etc. The number of inductors in series in 
each circuit is equal to the total number of inductors divided by the 
number of paths through the winding, and the greater the number 
of inductors in series the greater the induced electrical pressure, all 
other things remaining unchanged. 

If the lines of magnetic force cut by each inductor in one second 
be multiplied by the number of inductors in series the product 
will be equal to the total lines of magnetic force cut by all of the 
inductors in series in 1 second. This total number of magnetic lines 
of force cut by all of the inductors in series divided by 100,000,000 
gives the electrical pressure in volts, induced in each path of the 
armature winding. 

The only two factors which may be changed after the machine is 
instructed are the magnetic lines of force per pole and the revolu¬ 
tions of the armature. If the number of magnetic lines per pole re¬ 
mains constant, the induced pressure will vary directly as the speed 
of the armature. Likewise, if the speed remains constant the in¬ 
duced pressure will vary directly as the number of magnetic lines 
of force per pole. 

It is by varying the speed of the armature or the number of mag¬ 
netic lines of force that the output of a generator as to voltage 
is regulated. This will be explained later, 


CHAPTER XIII 


Fields and Field Windings for Generators 
and Motors 


I N the previous consideration of the production of an electrical 
pressure, in a conductor when it is moved across a magnetic 
field, as in the case of the armature of a generator, the presence 
of the field has been assumed and nothing has been said as to 
the method of providing the magnetic field. The term “field" 
is applied interchangeably to the magnetic lines of force between 



Fig. 114 —Magnetic circuit of 
simplest bipolar machine with 
one field coil at C 


Fig. 115 — Bipolar magnetic 
circuit with two field coils, one 
at C and one at Cl 


the pole faces of the field magnets and to the field magnets them¬ 
selves. There are two methods of producing the magnetic field 
for generators and motors, and these methods will be discussed 
in the following paragraphs: 

The permanent magnet provides perhaps the simplest method 
of producing a magnetic field. The field produced by a perma- 

































169 


FIELDS AND FIELD WINDINGS 

nent magnet is quite weak as compared to one produced by an 
electric current, and the magnetic field of the permanent magnet 
cannot readily be changed to meet changing requirements. The 
use of the permanent magnet as a means of producing a magnetic 
field is confined in motor cars almost entirely to the ignition 
magneto at the present time. 

If an electric current be passed through a winding surround¬ 
ing a piece of iron, the piece of iron will become magnetized by 
the action of the current. The degree to which the piece of 



coil 

iron becomes magnetized will depend upon the quality of the iron, 
the number of turns of wire in the winding and the current in the 
winding. The polarity of the pieces of iron will depend upon the 
direction in which the current passes around it, as previously ex¬ 
plained. The magnetic circuit of the generator and the motor is the 
path in which the magnetic lines of force exist and may assume 
many different forms, depending upon individual requirements. 

Types of Magnetic Fields 

The simplest form of magnetic field is one in which the arma¬ 
ture rotates between two magnetic poles, and it is known as a 
bipolar field. Three different forms of bipolar magnetic fields 
are shown in Figs. 114, 115 and 116. In Fig. 114 the winding 
in which the current producing the magnetic field flows is placed 



















170 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

around the part of the magnetic circuit marked C in the figure, 
This winding is always spoken of as a field winding. The mag¬ 
netic lines produced by the current in this winding circulate in 
the magnetic circuit indicated by the arrows, and they are all 
produced by a single coil of wire. This coil of wire is usually 
spoken of as a field coil. 

A bipolar magnetic field is shown in Fig. 115. There are two 
field coils, one about C and another about Cl. Both of these 
field coils tend to produce a magnetic field through the armature 


Fig. 117 —A four-pole magnetic circuit 
with four field coils 

in the same direction. There are two paths for the magnetic lines 
around the outside. 

A third type of bipolar magnetic field is shown in Fig. 116. 
In this case there is only one field coil, and it is placed around 
the part marked C. There are two paths for the magnetic lines 
around the outside, similar to the circuits shown in Fig. 115. 

A multipolar magnetic circuit of four poles is shown in Fig. 117. 
In this case there are four field coils and they are wound around 












FIELDS AND FIELD WINDINGS 


171 


the four parts marked C. It will be seen that two of these field 
coils act on any one of the four magnetic circuits. Alternate 
poles around the armature are of the same polarity, and adjacent 
poles are of opposite polarity. 

A four-pole magnetic circuit is shown in Fig. 118, but only two 
field coils are used instead of four, as in Fig. 117. These two 
field coils are placed about the part's of the magnetic circuit 
marked C in the figure. The general appearance of the magnetic 
circuit, as shown in Fig. 118, is quite similar to the one shown 
in Fig. 115, which is bipolar. A close comparison of the two will 
make the difference very noticeable. In Fig. 115 field coils about 
C and Cl both act to produce a magnetic field through the arma- 



Fig. 118 —A Jour-pole magnetic circuit with two field 
coils 

ture in the same direction, while in Fig. 118 the two field coils 
act to produce the magnetic field through the armature in oppo¬ 
site directions. As a result of the two field coils acting to pro- 
duce a magnetic field across the armature in opposite directions 
and on account of the nearness of the iron to the two sides of 
the armature, the magnetic lines pass through the paths indi¬ 
cated by the arrows. In this case only one field coil acts on any 
one of the four magnetic circuits. 

When the magnetic circuit is arranged similar to Figs. 115, 
116, 117, 118 and so forth so that the field winding is practically 
surrounded by the iron forming part of the magnetic circuit, it 
is called an iron-clad type. This type of construction is a better 






















172 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

protection for the field coils, and for this reason, all other things 
being equal, is much preferred to an open or exposed type of 
construction, as shown in Fig. 114. 

Parts of the Magnetic Circuit 

The magnetic circuit of almost every dynamo is composed of 
five parts, and they are: 

First, the armature core, which usually consists of a cylinder 
of laminated iron, mounted on a shaft and having its surface 
grooved to accommodate the armature winding. In the ring type 
of armature the core is in the form of a ring. The reason for 



laminating the armature core is to reduce the loss due to cur¬ 
rents in the iron core itself which are called eddy currents and 
which tend to heat the armature and decrease the efficiency of 
the machine. The armature core serves the double purpose of 
conducting the magnetic lines from pole to pole and at the same 
time supporting the armature winding. 

Second, the air gap, which is the clearance between the arma¬ 
ture core and the end of the poles. 

Third, the pole shoes, or pole pieces, which are the ends of the 
poles adjacent to the air gap. They are in some cases given a 
special shape in order to improve the distribution and arrange¬ 
ment of the magnetic lines forming the magnetic field. In some 



























FIELD? AND FIELD WINDINGS 173 

cases the pole shoes are made separate from the field core and 
bolted to the cores. 

Fourth, the field cores which are the parts of the magnetic 
circuit about which the field windings are placed. 

Fifth, the yoke, which is the outside portion of the magnetic 
circuit connecting the field cores. The yoke forms part of the 
magnetic circuit and at the same time serves as a mechanical 
support for the field cores and pole shoes, holding the pole shoes 
in their proper position with respect to the armature. 

Series Generator 

A series generator is one in which the armature and field wind¬ 
ings are connected in series, and any current supplied by the arma¬ 
ture passes through the field winding. The connections of a 



Fig. 120 —A shunt field; the field winding is in parallel with the 
outside circuit 


series generator are shown in Figure 119. The operation of such 
a machine, in brief, is as follows: Assuming that there is some 
residual magnetism in the fields due to their having previously 
been magnetized there will be a low electrical pressure induced 
in the armature winding when the armature is revolved in this 
weak magnetic field. This induced electrical pressure will not 
produce a current unless the terminals of the machine be con¬ 
nected directly together or by means of an external circuit. The 
current due to this low induced electrical pressure will flow 





























174 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

through the field winding and increase the strength of the mag¬ 
netic field, which in turn will increase the induced electrical pres¬ 
sure, which will increase the current, et'c. This operation would 
continue indefinitely and the induced pressure and current would 
both become dangerously high unless some means were provided for 
controlling them. As the current in the field winding increases, 
the number of magnetic lines in the field increases, but after a 
certain field strength has been reached, the magnetic lines cease 
to increase, due to a given increase in current, as rapidly as they 



Fig. 121 —A cumulative compound field, in which shunt and 
series windings act in the same direction 


did at first, and finally there is a very little increase in these 
lines, due to an increase in the field current, and the iron form¬ 
ing the magnetic circuit is said to be saturated. The series field 
winding is composed of a relatively small number of turns of wire 
of ample size to safely carry the maximum current the machine is 
designed to deliver. 

Shunt Generator 

A shunt generator is one in which the field winding is con¬ 
nected directly to the terminals of the armature as shown in Fig. 
120. The current in the field winding at any time is equal to the 
pressure between the brushes divided by the resistance of the 
winding and is independent of the current the generator may be 
supplying to a circuit connected to its terminals, unless the cur- 





























FIELDS AND FIELD WINDINGS 


175 


rent supplied changes the pressure between the brushes. The 
shunt generator will have a low pressure induced in it's armature, 
due to the residual magnetism in the fields. This pressure produces 
a current in the field winding, which in turn incrf.as**?* the strength 
of the magnetic field. This in turn increases the induced pressure, 
which increases the field current, etc. This operation continues 
until the magnetic condition of the iron is such that both the 
electrical pressure and field current become steady. In the series 
generator, the terminals of the machine had to be connected to- 



Fig. 122 —A differential compound winding in which the shunt and 
series field coils are wound in opposite directions, and thus 
buck each other 


gether in some way in order that the electrical pressure induced 
in the armature increase, while in the shunt generator it is not 
necessary to have the terminals connected in order that the elec¬ 
trical pressure induced in the armature increase. In fact, it is 
best to have the terminals entirely disconnected from all circuits. 

The shunt field winding is composed of a relatively large num¬ 
ber of turns of small wire. The current the shunt field winding 
carries is usually a small part of the total current the machine is 
capable of generating. 

Compound Generator 

A compound generator is a combination of a series and a shunt 
generator. When the magnetizing action of the series aijd shunt 
field are in the same direction as shown in Fig. 121, it is called a 



































176 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

cumulative compound generator. If the magnetizing action of 
the series and shunt fields are in opposite directions, as shown in 
Fig. 122, it is called a differential compound generator. When the 
shunt winding is connected directly to the brushes, the machine is 
called a short shunt compound machine, as shown in both Figs. 
121 and 122. If the shunt winding is connected across both the 
armature and series field, the machine is called a long shunt com¬ 
pound machine. The action of these field windings will be dis¬ 
cussed at length under the subject of generator output. It is by 
these field windings in some lighting generators that the current 
to the battery and lights is kept constant. 


CHAPTER XIV 


Generator Output and Purpose of Cutout 


S explained in the previous section, the electrical pressure 



generated in the armature winding of a generator depends 
upon the number of wires on the surface of the armature, the 
manner in which these wires are interconnected, which deter¬ 
mine the number of different circuits through the armature wind¬ 
ing; the number of magnetic lines, called the magnetic flux, en¬ 
tering or leaving the armature at the different poles; the number 
of magnetic poles forming the magnetic circuit; and the speed at 
which the armature is revolving in the magnetic field. After a 
generator is constructed, the number of magnetic poles, the num¬ 
ber of wires on the surface of the armature and the number of 
different circuits through the armature are all fixed, while the 
speed and number of magnetic lines, or magnetic flux, per pole 
may either or both be changed. 

The speed of the generator, of course, depends upon the speed 
of the device driving it and the manner in which the generator is 
connected to this device. The armature of the generator may be 
mounted on the shaft of the driving device or it may be geared 
or connected to the shaft by a clutch or chain. In some cases 
the construction of the driving clutch is such that the armature 
of the generator never exceeds a predetermined speed, regardless 
of the extent to which the speed of the driving device increases. 

The magnetic flux per pole depends upon the form of the mag¬ 
netic circuits, the kind of material composing the magnetic circuit 
and the number of ampere-turns acting on each magnetic pole. 
The number of ampere-turns, magnetizing effect, of a coil is equal 
to the product of the number of turns in the coil and the current 
in these turns. After the machine is once constructed, the form 
of the magnetic circuit, the kind of material composing the mag¬ 
netic circuit and the number of turns in the different windings 


178 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

about the fields are all fixed and constant in value. The only way 
then—neglecting armature reaction which will be explained later— 
that the magnetic flux entering or leaving the armature at the 
different poles may be changed is by varying the value of the 
current in the field windings. 

Assuming for convenience that the magnetic flux per pole 
remains constant, then the electrical pressure generated in the 
armature winding will vary directly as the speed of the armature, 
starting at nothing for no speed and increasing directly as the 
speed increases. The relation of the electrical pressure gener¬ 
ated to the speed is shown graphically in Fig. 123, in which speed 



SPEED Ill REVOLUTIONS PER MINUTE 


Fig. 123 —Relation between 
armature speed of a generator 
and the pressure it generates. 
The dotted line shows the re¬ 
lation between armature speed 
and the pressure it generates 
when the field is weakened. 



Fig. 124 —Relation between 
the magnetic flux in a gener¬ 
ator and its generated pres¬ 
sure, at constant speed. The 
dotted line shows the relation 
between magnetic flux per pole 
and generated pressure when 
the speed is decreased. 


is measured along the horizontal and pressure along the vertical. 
If the magnetic flux per pole be changed, say decreased, then 
there will be a corresponding decrease in the pressure generated 
for the different speeds as indicated by the dotted curve. 

If the speed of the machine be maintained constant and the 
magnetic flux per pole be increased, there will be an increase in 
the electrical pressure in the armature winding as shown graphic¬ 
ally in Fig. 124, in which magnetic flux is measured along the 
horizontal and pressure along the vertical. If the speed of the 
machine be changed, say decreased, then there will be a corre¬ 
sponding decrease in the pressure generated for the different 
values of magnetic flux per pole as indicated by the dotted curve 







































GENERATOR OUTPUT; PURPOSE OF CUTOUT 179 

The magnetic flux per pole does not have a definite relation to 
the current in the field winding surrounding the pole, due to the 
fact that the permeability of the iron forming the magnetic cir¬ 
cuit is not constant but depends upon the degree to which it is 
magnetized. You can think of the permeability of the iron as 
being its property to conduct magnetic flux as compared to the 
ability of air to conduct magnetic flux, which for convenience is 
assumed to have a permeability of one. The relation between the 
magnetic flux per pole and the current in the field winding is 
shown in !Fig. 125. It will be seen from an inspection of this curve 



CURRENT IN FELD "WINDING 
OF A GENERATOR 


Fig. 125 —Flow the magnet¬ 
ization of a generator field pole 
increases with the increase in 
current in its field winding. 
The point A indicates the sat¬ 
uration point 



SPEED IN REVOLUTIONS PER MINUTE 


Fig. 126 —Relation betiveen 
the generated pressure and 
armature speed of a shunt gen¬ 
erator. Above a certain point 
A the pressure increases more 
slowly with increase in speed 


that the magnetic flux at first increases very rapidly, due to an 
increase in the value of the field current, but after the flux has 
reached a value represented by the point A in the curve the 
increase due to an increase in field current is decidedly less. When 
the magnetic flux has reached the value represented by the point 
A, the magnetic circuit is said to be saturated and above this point 
there is very little increase in flux even though there be a large 
increase in the field current. 

Operation of Self-Excited Shunt Generator 

The connections of the self-excited shunt generator, that is, one 
supplying its own field current, have been given. When the arma- 








































180 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ture starts to rotate there is one electrical pressure generated in 
it's winding, due to the residual magnetic flux in the magnetic 
circuit, which produces a current in the field winding and this 
current increases the magnetic flux per pole. As a result of both 
the speed and magnetic flux increasing, the generated pressure 
increases more rapidly than if the speed alone were to increase. 
After the magnetic flux has reached a certain value, however, the 
magnetic circuit becomes saturated and then there is very little 
increase in the magnetic flux per pole even though the field current 
continues to increase. 

After the magnetic circuit has become saturated, the increase 
in generated pressure is due almost entirely to the increase in 
speed. The relation between generated pressure and speed is 
shown in a general way in Fig. 126. Up to the point A on the 
curve there is a very rapid increase in generated pressure as the 
speed increases, since the magnetic flux per pole and the speed 
are both increasing. From the point A, however, the generated 
pressure increases less rapidly, as the magnetic circuit is practically 
saturated and the speed alone is increasing. 

Constant Current and Constant Voltage Output 

The output of a generator in watts is equal to the product of 
the current the generator is delivering in amperes and the pres¬ 
sure at which this current is delivered in volt's. The current 
delivered by a generator to a circuit containing no other source 
of electrical pressure is equal to the generated pressure in the 
armature of the generator divided by the total resistance of the 
circuit, including the connecting leads and the resistance of the 
armature of the generator itself. If the pressure generated in 
the armature winding of the generator remains constant, the 
current supplied by the generator will vary inversely as the 
resistance of the circuit in which the generator is connected. 
That is, if the resistance of the circuit increases, the current in 
the circuit will decrease and if the resistance of the circuit 
decreases, the current will increase. 

If the pressure generated in the armature winding of the gen¬ 
erator changes in value, the resistance of the circuit remaining 
constant, there will be a corresponding change in the value of the 
current. That is, if the pressure increases, the current will in¬ 
crease and if the pressure decreases, the current will decrease. 
If, however, the pressure generated in the armature of the gen- 


GENERATOR OUTPUT PURPOSE OF CUTOUT 181 

erator and the resistance of the circuit both changes, then the 
current at any time is equal to the pressure at that time divided 
by the value of the resistance at that time. 

When the output of a generator is at a practically constant 
current, the pressure varying in value or not as the case may be, 
the generator is spoken of as a constant current generator. When 
the output is at a practically constant pressure, the current vary¬ 
ing in value or not as the case may be, the generator is spoken 
of as a constant voltage generator. 

Purpose of the Cutout 

The electrical generator in its application to the motor car is 
almost always used in combination with a storage battery. The 
generator is used to charge the battery and to produce a current 



Fig. 127 —Simplest connection of generator and storage battery. 
When generator is not supplying current, the storage battery dis¬ 
charges through it 


in the various electrical devices on the car while the generator is 
in operation. The battery serves as a sort of reservoir in which 
electrical energy may be stored and then used when the generator 
itself is not operating. A battery and generator are shown con¬ 
nected in series in Fig. 127. The positive terminal of the genera¬ 
tor is connected to the positive terminal of the batteries and their 
negative terminals are connected together. The effective pres¬ 
sure acting in such a circuit is equal to the difference in the 
pressure produced by the generator and the pressure produced 
within the battery. 

If these two pressures are equal, the value of the effective pres¬ 
sure will be zero and there will be no current in the circuit. If 
the pressure produced by the generator exceeds in value the pres¬ 
sure produced by the battery, there will be an effective pressure 














182 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

acting in the circuit and its direction will correspond to that of 
the larger pressure, or the pressure of the generator. The current 
produced by this effective pressure will charge the battery, and 
the value of the current will be equal to the effective pressure 
divided by the total resistance of the circuit, including the inter¬ 
nal resistance of the battery, the resistance of the connecting 
wires and the resistance of the armature winding of the generator. 

If the pressure generated in the armature winding of the gen¬ 
erator is less than the pressure of the battery, then the effective 
pressure will be in the direction of the battery pressure and the 
battery will discharge instead of being charged. The value of 
the current will, as in the previous case, be equal to the effective 
pressure divided by the total resistance of the circuit. 



Since the pressure generated in the armature winding of the 
generator may vary in value from zero on up, depending upon its 
speed and field control, it is apparent that some means must be 
provided for controlling the connection between the generator 
and the battery in order that the battery will not be allowed to 
discharge through the generator when the pressure of the gener¬ 
ator becomes lower than the pressure of the battery. The object 
of the cutout may be understood by use of the simple diagram 
given in Fig. 128. An electromagnet M has a winding Qf a large 
number of turns, and this winding is connected directly to the 
terminals of the generator. The resistance of the winding of 
this electromagnet is usually such that a very small current passes 





















GENERATOR OUTPUT; PURPOSE OF CUTOUT 183 

through it in comparison to the total current output of the gener¬ 
ator. An armature A pivoted at its left-hand end and carrying a 
contact point on its right-hand end is mounted near the core of the 
electromagnet. 

This armature is usually held away from the core of the electro¬ 
magnet by means of the spring and the movable contact point C 
is not in contact with the stationary contact point. The connec¬ 
tions of the generator and battery are clearly indicated in the 
figure. Now as the pressure generated in the armature of the 
generator increases there will be an increase in the current in 
the winding of the electromagnet M, and the tension of the spring 
S may be so adjusted that the armature A pulls up at the desired 
pressure. The tension in the spring S is usually so adjusted that 
the generator pressure is a little higher than the battery pressure 
when the circuit is completed, and the battery will always start 
to charge. When the pressure of the generator decreases, due to 
any cause, there is a decrease in the current in the winding of 
the electromagnet M and the magnet pull it produces on the arma¬ 
ture A decreases in value. If the pull of the spring S exceeds the 
magnetic pull the armature will move away from the core of the 
electromagnet and the circuit between the battery and generator 
will be broken at the contact C. 

The cutout whose connections and arrangement are shown in 
Fig. 128 would be satisfactory for closing the electrical circuit 
connecting the generator and battery, but would not open it properly 
in practice for the following reasons: In theory the spring S would 
pull the armature away from the core of the electromagnet when 
the electrical pressure generated in the armature of the generator 
dropped below a value which would produce the necessary current' 
in the winding to hold the armature up. The following action, 
however, takes place in actual practice: When the electrical pres¬ 
sure of the generator exceeds the electrical pressure of the battery, 
the direction of the current in the battery, generator and winding 
of the electromagnet will be as indicated by the three arrows in 
Fig. 129. If there is a decrease in the electrical pressure of the 
generator, due to any cause, or an increase in the electrical pressure 
of the battery and the two pressures become equal in value, there 
will be no current in the circuit composed of the generator and the 
battery. 

If the winding of the cutout be connected when the pressures of 


184 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the generator and battery are equal, a current will be established 
in the winding, which will be supplied jointly by the generator and 
battery, and the direction of the currents will be as indicated in 
Fig. 130. The division of the total current supplied the cutout’ 
between the generator and the battery will depend upon the rela¬ 
tion betwen their internal resistances. When the electrical pres¬ 
sures within the generator and the battery are each exactly the 
same and their internal resistances are equal, then each of them 
will supply one-half of the total current in the winding of the 
cutout. If their internal resistances are not equal, their pressures 
being equal, then the one having the smaller internal resistance will 
supply the larger part of the total current in the winding of 
the cutout. 


When the electrical pressure in the armature winding of the 



Fig. 129 —Direction of currents when battery is charging. The 
electrical pressure of the generator exceeds that of the battery 


generator is less than the electrical pressure in the battery, then 
Ithe battery starts to discharge and sends a current through the 
armature of the generator in the opposite direction to the pressure 
generated in the armature, as indicated in Fig. 131, thus causing 
a motor action to take place. The degree of this motor action will 
depend upon how much current is produced in the armature wind¬ 
ing, which in turn will depend upon the difference in the pressure 
in the armature of the generator and the pressure of the battery, 
or the effective pressure, divided by the total resistance of the 
entire circuit. It is interesting to note that the battery will 
supply a current to the winding of the cutout and that the 
direction of this current in the winding of the cutout is the 
same as when it was Supplied by the generator. This results 
\n the armature of the cutout remaining drawn up, and the circuit 












GENERATOI OUTPUT; PURPOSE OF CUTOUT 185 

between the generator and the battery will remain closed even 
though the battery is discharging through the armature of the 
generator. The cutout will remain closed at the comparatively 
low pressure of the battery when almost discharged, on account 
of the fact' that it does not take as much of a current to hold the 
armature in place after it is once drawn up as it does to draw 
it up in the first place, when there is quite an air gap between it 
and the core of the electromagnet. 

The connections outlined in Fig. 132 are used in order to over¬ 
come the fault just pointed out. The cutout is provided with two 
windings instead of a single winding. One of these windings, M, 
called the shunt winding, is connected directly to the terminals of 
the dynamo, or rather the two leads from the dynamo, and the 



BATTERY 


f 


CVTOVT 


Fig. 130 —When the electrical pressures of the generator and the 
}battery are equal, the current to the cutout will he supplied hy 

hoth 


current in this winding will be equal to the pressure between the 
two main line wires divided by the resistance of the winding. The 
other winding, called the series winding, is composed of a smaller 
number of turns than the shunt winding and the wire used in this 
winding is usually quite a bit larger than the wire used in the 
shunt winding. The series winding is connected directly in the 
circuit connecting the generator and battery and carries whatever 
current passes through the battery. The connection of the series 
winding is such that the direction of the current through it is 
around the eore of the electromagnet in the same direction as the 
current in the shunt winding when the battery is charging. When 
the pressure of the generator has built up to the proper value the 
shunt winding draw r s up the armature and the battery starts to 
charge. 
















186 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Let us now consider what happens when the pressure of the 
generator drops below the pressure of the battery. Just as soon as 
the generator pressure becomes less than the batt'ery pressure, the 
battery will start to discharge and the current in the series coil 
will be reversed in direction. The current in the shunt coil will, 
however, remain in the :ame direction as previously explained, 
which results in the magnetic action of the two coils being opposed 
to each other. Now, as the pressure of the generator decreases, 
there will be an increase in the discharge current from the battery 
and the magnetic action of the series coil will increase. Since the 
magnetic action of the series and shunt coils are opposed to each 
other when the battery is discharging, the difference in their 
effects or the resultant magnetic action acting on the core of the 



Fig. 131 —Direction of current when the battery is discharging. 
The pressure of the generator has dropped below that of the battery 


electromagnet will decrease in value as the current in the series coil 
increases in value. The resultant magnetizing action of the two 
coils will be zero when the product of the number of turns and the 
current these turns contain is the same for both coils. The action 
of the spring S, however, draws the armature away from the core 
when the resultant magnetic action has been reduced to a certain 
predetermined value and the circuit connecting the generator and 
the battery is broken. In order that the circuit be closed again it 
is necessary that the pressure of the generator increase in value 
until ample current is produced in the shunt winding to draw up 
the armature. 

The series coil performs another useful purpose, in addition to 
the above, in the satisfactory operation of the cutout. If a cutout 
having only a shunt coil were made, there would be a tendency for 
the cutout to open and close at something like the same value of 















GENERATOR OUTPUT; PURPOSE OP CUTOUT 187 

generated pressure. If the car were driven at such a speed that 
the generated pressure would result in the cutout opening and clos¬ 
ing continuously, due to a more or less balanced relation between 
the magnetic and spring pulls on the armature, the contacts would 
be seriously injured, due to the hammer action at the contacts and 
also due to excessive sparking. The series coil prevents this occur¬ 
ring in the following manner; the shunt coil acts alone in closing 
the cutout’, as there is no current in the series coil until the cutout 
contact is closed and the magnetic pull of the shunt coil is just 
sufficient to overcome the spring pull on the armature when the 
armature is drawn up. As soon as the circuit is closed, assuming 



Fig. 132 —Complete electromagnetic cutout. The two windings 
tend to equalize the pressure at the time of the opening and closing 

of the cutout 


the adjustment is properly made, the series coil will assist the 
shunt coil in holding the armature. If the electrical pressure now 
decreases in value, the cutout contacts will remain closed until the 
combined magnetic action of the shunt and series coils are equal 
to or a little less than the magnetic action of the shunt coil alone 
at the time the contacts were first closed. In practice the difference 
in car speeds at the time of closing and opening of the cutout 
contacts is something like 2 miles per hour, the speed at which they 
open being less than the speed at which they close. 

Two-Pole Cutout 

The cutout’s described thus far have only one set of contacts and 
hence open only one side of the charging circuit. Such cutouts are 
called single-pole cutouts. In some cases the construction of the 
cutout is such that both sides of the charging circuit' are opened 



































188 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

and closed by the operation of the cutout. Such cutouts are called 
two-pole cutouts. An example of a two-pole cutout is shown in 
Fig. 133, which gives the wiring diagram of the cutout made by 
the Leece-Neville Co. There is a current produced in the shunt 
winding S which draws up the armature A and closes the two sets 
of contacts Cx and C 2 , thus completing the circuit between the 



Fig. 133— Tivo-pole cutout. It is so constructed that both sides of 
the charging circuit are opened and closed by its operation 


generator and battery through the heavy series winding around the 
core of the electromagnet. When the combined magnetic effects 
of the shunt and series windings is reduced, due to the decrease in 
the pressure generated in the armature of the generator, the springs 
Px and Po push the armature away from the core and open both 
sets of contacts, thus breaking the electrical connection between 
the generator and the battery on both the positive and negative 
sides. 

Arrangement of Windings on Cutout 

Separately mounted cutouts of the two-pole type usually have 
three terminals: one, marked D, leading to the dynamo only; 
another, marked B, leading to the battery only; and a third one, 





























































GENERATOR OUTPUT; PURPOSE OF CUTOUT 189 

marked DB, which is attached to both the dynamo and battery. 
In the two-pole type of cutout there are usually four terminals; 
two go direct to the battery and two direct to the generator. 

In the majority of cases the series and shunt windings are placed 
on the one single core; but in some cases two separate cores are pro¬ 
vided, one for the series winding and one for the shunt winding; 
while in other cases two cores are provided and part' of each of the 
shunt and series windings placed on each of the cores. The two 
cores on which the windings are placed may be located side by side 
or one may be placed above the other. 

In some of the systems the arm that supports the movable con¬ 
tact point carries one or more of the electromagnets. A good 
example of a cutout of this type is the one found in the Adlake 
equipment. In this case there are two sets of electromagnets, one 
set being stationary and the other set movable. The mounting for 
the movable set of magnets carries one of the contacts, and this 
contact point makes electrical connection with the stationary con¬ 
tact' when the movable magnets are drawn up against the stationary 
magnets directly above them. No spring is used to open the con¬ 
tacts, the weight of the movable magnets serving the purpose of 
the spring. 

Location of Cutouts 

The cutout may be found in any one of a number of different 
places, depending on the design and make of the equipment. In 
some cases it’ is mounted in a special housing provided for it and 
attached to the generator; it may be placed inside the generator 
frame in the brush and commutator compartment or in the space 
between the magnetic poles. The location of the cutout inside the 
generator or in a housing attached to it reduces the length of the 
wires between the cutout and generator to a minimum, and only 
two wires need be run from the generator in the two-wire system 
or one wire in a one-wire system. The cutout is sometimes located 
under the front seat, under the floor boards, on the front side of 
the cowl board, with the regulating device, or with the starting, 
lighting or ignition switch. 

Manual Cutouts 

In the manual type of cutout the connection between the gen¬ 
erator and battery is controlled by a switch that is attached to the 
button, handle or lever of the starting switch or the ignition 


190 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

switch. It is customary to attach the ignition switch to the start¬ 
ing switch when this type of cutout is used, and for this reason it 
might be said that a manually operated cutout will always be 
interconnected with the ignition switch in such a manner that the 
circuit connecting the generator and battery will be closed when 
the ignition circuit is closed and opened when the ignition circuit 
is opened. A diagrammatic representation of a system of this kind 



Fig. 134 —Manual cutout showing position of switch, H, when the 
engine is idle 

is shown in Fig. 134. The switch in this case is eomposed of a 
curved blade B provided with a handle H and pivoted at the point 
O. The position of the handle shown in the figure corresponds to 
an idle engine. The two contact's marked Ci and C 2 are for the 
purpose of grounding the magnets and thus cutting off the ignition. 
The dynamo in this case operates as a motor when the main switch 
is closed, the shunt and series fields acting upon the magnetic 
circuit in the same direction. As the machine speeds up, the pres¬ 
sure in it’s armature will increase, and when it exceeds the pressure 
of the battery, the battery will start to charge. When the battery 
is charging, the shunt and series magnetic fields act on the magnetic 
circuit of the dynamo in the opposite direction with respect to each 
other. The switch may be placed in a position between the two 
extreme positions, which results in the ignition being operative but 
the battery entirely disconnected. The shunt’ field' is also opened, 
which prevents there being a pressure generated in the armature 
of the generator. Rotary switches may be used instead of the 
knife type shown in the figure. The principles involved in the 
manual cut'out have been used with Westinghouse, Bijur, Delco, 
Dyneto and Entz equipment. 











CHAPTER XV 


Regulation of Generator Output 


S previously explained, the output of a generator in watt's is 



equal to the product of the current in amperes the generator is 
delivering and the pressure in volts between the terminals of the 
machine. Either the current or pressure may vary in value, the 
other remaining practically constant, or both may vary in value. In 
the majority of cases, however, an attempt is made to maintain either 
the pressure, frequently called the voltage, or the current practically 
constant in value, thus giving two main types of systems known as 
the constant-voltage and constant-current systems, respectively. 

There are four different methods of regulating the output of a 
generator and they may be classified as follows: 

(a) Inherent Regulation. This type of regulation is that ob¬ 
tained as a result of the characteristics of the generator without 
the use of any moving parts. In this class are included cumulative 
and differential series field windings and a type of generator hav¬ 
ing one or more brushes in addition to those required in delivering 
a current to the battery and known as a third-brush machine. The 
field current for the shunt winding is taken from this third brush 
and one of the main brushes. 

(b) Electromagnetic Regulation. This type of regulation is 
produced by the action of electromagnets which may act to increase 
the resistance of the shunt field circuit or to open the field circuit 
or to change the connections of the field windings. 

(c) Mechanical Regulation. This type of regulation is produced 
by the action of centrifugally operated governors which may act 
to prevent the speed of the generator increasing above a certain 
definite value or to insert a resistance in series with the field wind¬ 
ing or in series with the generator and the battery. 

(d) Regulation by Ampere-Hour Meter. This type of regula¬ 
tion is produced by means of an ampere-hour meter, which changes 


192 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the resistance of the field circuit, depending upon the number of 
ampere hours that may pass into or out of the storage battery. 

All the above types of regulation are found in many different 
applications and in combination with each other, giving rise to 
numerous distinctive types as used by the different manufacturers 
of motor car generators. 

Cumulative Action of Series and Shunt Field Windings 

When the magnetizing action of the current in the series and 
shunt field windings of a generator are both in the same direction, 
the action is said to be cumulative, and the generator is called a 
cumulative compound-wound machine. A compound-wound machine 
of this kind is used in combination with a constant-speed machine. 
A good example of such a combination is found in some of the older 
types of equipment manufactured by Gray & Davis, in which the 
generators were driven at a constant speed by means of a cen¬ 
trifugal clutch. 

A diagrammatic scheme of connections for this type of regula¬ 
tion is shown in Figure 135. When there are no lamps lighted, the 
shunt winding is acting alone and sufficient pressure is generated 
in the armature winding to overcome the pressure of the battery 
and produce a charging current. When the lamps are turned on, 
the current through them passes through the series field and in¬ 
creases the magnetic field in which the armature is rotating, thus 
increasing the electrical pressure generated. By a proper adjust¬ 
ment of the turns in the series field in relation to the current taken 
by the lamps, it is possible to cause the generator to carry the lamp 
load and to continue to charge the battery at the same rate it was 
charging the battery before the lamps were turned on. 

Differential Action of Series and Shunt Field Windings 

When the magnetizing action of the current in the series and 
shunt field windings of a generator are in opposite directions, the 
action is said to be differential, and the generator is called a differ¬ 
ential compound-wound machine. A good example of inherent regu¬ 
lation in which the shunt and series fields produce opposing mag¬ 
netizing effects is found in one type of equipment made by the 
Auto-Lite Co. A diagrammatic scheme of connections for this type 
of regulation is shown in Figure 136. The action in brief is as 
follows: The voltage of the machine is built up with an increase 
in speed and shunt field current until the cutout connects the gen- 


REGULATION OF GENERATOR OUTPUT 


193 


erator to the battery. After this connection is made, a current will 
be established in the series field winding in such a direction that 
its magnetizing action is opposite to that produced by the shunt 
field, and hence the magnetic field is weakened. With a further 
increase in speed there will be an increase in generated pressure in 
the armature of the generator, which will cause an increase in the 
value of the current produced in the series winding and battery and 


•5HUNT SERIES 



Fig. 135 —Regulation pro¬ 
duced by cumulative action of 
series and shunt fields. The 
series field carries only the cur- 
rent supplied to the lamps 


•SHUNT .SERIES 



Fig. 136 —Regulation pro¬ 
duced by differential action of 
series and shunt fields. The 
series field carries the total cur¬ 
rent supplied by the generator 


also an increase in the current in the shunt field winding. Since the 
magnetizing action of the series field is opposed to the magnetizing 
action of the shunt field, the increase in generated pressure due to 
an increase in speed will not be as great when both fields are acting 
as when the shunt field is acting alone. In this case all the current 
supplied by the dynamo passes through the series field winding. 

Bucking Series Field Winding 

The bucking series field winding is really a differential or reversed 
series field winding, the only difference being that the series field 













































194 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

winding does not carry all or necessarily a definite part of the 
current delivered by the generator. The operation of the bucking 
coil may be explained by reference to Fig. 137, which is exactly the 
same as Fig. 136 with a coil of iron wire W connected in parallel 
with the series field winding. The resistance of iron wire increases 
with an increase in temperature and this increase is very rapid 
after a certain temperature has been reached. Now, when the 
current delivered by the generator is small practically all the current 
passes through the coil W, as its resistance is much less than the 
resistance of the series field winding. As the current delivered by 
the generator increases, the temperature of the iron wire will in- 


<SHUWT cSERIES 



Fig. 137 —Regulation produced by bucking-coil. A coil whose 
resistance changes icith temperature is connected in parallel with 
the series field, which acts differentially with respect to the shunt 
field. Here the shunt is shown connected directly across the 
brushes for simplicity, but in practice the terminal shown here 
connected to the upper brush is connected to the battery line be- 
ttveen the battery and the juncture of the series field and ballast 
coil. This gives a more even pressure 

crease. Hence, there is an increase in the resistance it offers, and 
as a result, a larger part of the total current delivered by the gen¬ 
erator will pass through the series field winding. This increase in 
current in the series field prevents as large an increase in generated 
voltage as would occur if no series field were used. When the 
current supplied by the generator is reduced, the temperature of 
the iron wire is lowered and the division of the total current between 
the series field and coil W is restored to its previous value. This 
system of regulation is used on some of the equipment of the 
Bosch Magneto Co.; also on the equipment of the Rushmore Dynamo 
Works, which is now a part of the Bosch Magneto Co. 































REGULATION OF GENERATOR OUTPUT 


195 


Third-Brush Machine 

In order to understand the operation of the third-brush machine 
it will be necessary to make a brief study of the magnetizing action 
of the current in the armature winding of a generator in combina¬ 
tion with the magnetizing action of the current in the field windings. 

A cross-section through the armature and poles of a two-pole 
generator is shown in Fig. 138. The wires on the surface of the 
armature are represented by twenty small circles spaced equal dis¬ 
tances apart around the outside of the large circle which is sup¬ 



posed to represent the armature core. As a matter of fact, there 
are more than twenty wires on the surface of the armature, but 
this number has been used to simplify the diagram, the results 
being exactly the same. The polarity of the poles is indicated by 
N and S; the polarity of the armautre core by N1 and SI; and the 
direction of the magnetic field by the small arrows. 

If the armature be revolved in the clock-wise direction, as indi¬ 
cated by the large curved arrow at the top of the figure, an elec¬ 
trical pressure whose direction is toward the observer will be 
















































196 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

induced in the wires on the left-hand side of a vertical line through 
the armature, and an electrical pressure whose direction is away 
from observer will be induced in the wires on the right-hand side 
of the armature. An electrical pressure, or current, toward the 
surface of the paper is represented by a plus (+) sign and one 
away from the observer by a minus (—) sign. If you will think of 
the + and — signs as being respectively the feathered end and 



Fig. 139 -Cross-section through fields and armature of a tu o- 
pole generator, showing magnetic field produced by armature cur¬ 
rent alone 


flattened point of an arrow pointing along the wire, the diagram 
becomes plain. The direction of the current always can be found 
by the Right-Hand Rule mentioned previously. 

The wires on the surface of the armature are all interconnected 
by the commutator segments, and a current will be produced in 
them when the brushes resting on the commutator are connected 
to a closed electrical circuit. This current in the armature will 
produce a magnetizing action just the same as the current in the 
field windings. The magnetic effect of the current in the armature 
winding of the generator may be investigated by sending a current 














REGULATION 01?’ GENERATOR OUTPUT 197 

through the armature from an outside source, such as a battery, in 
the same direction as the current the generator itself would pro¬ 
duce, with the armature standing still and no current in the field 
windings. The general form of the magnetic field produced by the 
armature current would correspond to the dotted lines shown in 
Fig. 139, and its direction through the armature would be from 
the lower toward the upper side. The polarity of the armature is 



indicated by N and S in the figure. As a matter of fact, this 
magnetic field can never exist alone, but the magnetizing effect of 
the armature current combines with the magnetizing effect of the 
field current to form a resultant field whose general form will cor¬ 
respond to the one shown in Fig. 140. 

The magnetizing effects of the armature and field currents may 
be considered just the same as two mechanical forces which are 
acting on an object at right angles to each other. Thus the direc¬ 
tion of the magnetizing force of the field current may be represented 
by the line marked F in Fig. 141, and its direction corresponds to 
the direction in which the arrow head points. Likewise, the mag- 











198 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

netizing effect of the armature current may be represented by the 
line A, and its direction corresponds to the direction in which the 
arrow head points. The two forces combine to form the resultant 
force R, which produces the magnetic field whose direction cor¬ 
responds to the arrow head. The angle the resultant R makes with 
the horizontal will depend upon the relation between the two forces, 
A and F, the larger the value of A the greater the angle. This 
magnetizing action of the armature current is called armature 
reaction. 

If the brushes be placed on the commutator in such a position 
that they rest on segments that are connected to conductors on the 



Fig. 141 —The combined 
magnetizing activities of arm¬ 
ature and field currents, A and 
F form the resultant magnetic 
activity R 



commutator bars 


Fig. 142 —Diagram of armature tvinding on a Delco generator. 
Each coil is represented by a single ,turn 


surface of the armature in which there is no induced electrical 
pressure, a maximum Voltage for a given field strength and speed 
will exist between them. The brushes A and B in Fig. 138 are 
shown in a position for maximum voltage. If a third brush C be 
placed on the commutator midway between the brushes A and B, 
the voltage between A and C will be exactly the same as the voltage 
between C and B, because the same amount of magnetic flux is cut 
by the conductors in moving from C to A as is cut in moving from 
B to C. When the magnetic field is distorted, due to armature 

























































































REGULATION OF GENERATOR OUTPUT 


199 


reaction, as shown in Fig. 140, the voltage between B and C will 
be less than the voltage between C and A, since there is a greater 
amount of magnetic flux cut by the conductors in moving from 
C to A than is cut by them in moving from B to C. 

The position of the brushes shown in Fig. 138, 139 and 140 does 
not correspond to their actual position in practice, on account of 
having the end connections of the armature winding all of prac¬ 
tically the same length. The armature winding of a Delco gen¬ 
erator is shown diagrammatically in Fig. 142. The winding can 
be imagined as being removed from the surface of the armature and 
laid out flat with the pole pieces shown shaded. The commutator 
segments are spread out and shown in their proper relation to the 





Fig 143 —Connection of shunt field on third-brush machine. The 
main brushes arc opposite the centers of the poles 


armature conductors. The various coils composing the armature 
windings are connected together at the commutator segments, and 
in order that the ends of these coils leading out to the commutator 
segments be of the same length and form, it is necessary that the 
segments to which the terminals of a coil are connected be as near 
the center of the coil as possible. For example, starting with seg¬ 
ment number two and tracing through a coil, you end up at seg¬ 
ment number three, etc., and segments two and three are placed' 




















200 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

opposite the centers of the coils which are shown connected to them 
in the diagram. 

In order to simplify the diagram each coil is represented as 
being composed of a single turn. With this type of connection the 
main brushes will be in positions opposite the centers of the poles, 
as shown in Fig. 142 and 143. The voltage between the brushes 
B and C will become a smaller and smaller part of the total voltage 
between the brushes A and B as the magnetic field of the generator 
is distorted, due to the magnetizing action of the armature current. 



Fig. 144 —Curves showing relation of shunt current and delivered 
current to the speed of car in miles per hour and speed of generator 
in revolutions per minute for a Delco third-hrush generator 

The shunt field winding is connected to the brushes B and C, and 
the current in this winding decreases with an increase in speed of 
the generator, as shown by the curve marked shunt field current 
in Fig. 144. The current delivered by the generator increases in 
value with an increase in speed up to a certain maximum value and 
then starts to decrease with further increase in speed, due to the 
weakening of the magnetic field, as shown by the curve in Fig. 144. 

Electromagnetic Regulation 

Inserting Resistance in Field Circuit Intermittently by Means 
of a Magnetic Vibrator: The principal of this type of regu- 




































REGULATION OF GENERATOR OUTPUT 


201 


lation can best be understood by referring to Fig. 145, which 
shows in a diagrammatic form the electrical connections of the 
generator, battery and regulator. The regulator consists of an 
electromagnet with a winding, M, of wire large enough to carry 
all the current delivered by the generator and connected directly 
in series with the generator and battery. An armature, A, is 
mounted near one end of the elctromagnet and normally held 
away from the core of the electromagnet by means of a spring, S. 
When the armature moves toward the core of the electromagnet 
a contact is broken at C. The generator is of the shunt type 
with one terminal of the field winding connected to one terminal 
of the machine and the other terminal connected to the remain¬ 
ing terminal of the machine with the contact, C, on the regulator 
in series. A resistance, R, is connected across the terminals of 
the contact C and when this contact is opened, due to the action 
of the electromagnet, the resistance R is in series with the 
shunt field winding. 

The actual operation of the regulator is as follows: As the 
generator speeds up the electrical pressure between its terminals 
increases, and when it has reached a value ample to charge the 
battery the cutout will connect the generator and battery to¬ 
gether and the battery will start to charge. With a further in¬ 
increase in the electrical pressure between the terminals of the 
generator, the current delivered to the battery will increase, and 
unless some means be provided for limiting the value of the pres¬ 
sure of the generator this current will become excessively high 
and do damage to both the generator and battery. As the cur¬ 
rent in the winding of the electromagnet increases in value, there 
is an increase in the magnetic attraction the core of the electro¬ 
magnet has upon the armature, and when this attraction is suffi¬ 
cient to overcome the action of the spring S the armature will 
move and break the contact C and introduce the resistance R in 
series with the field winding. When the resistance R becomes a 
part of the shunt field circuit, the current in the field winding 
is reduced in value, which causes a reduction in the strength of the 
magnetic field in which the armature is revolving and, hence, a 
reduction in the electrical pressure generated in the armature 
winding. 

This reduction in electrical pressure results in the value of 
the current supplied to the battery, which passes through the 


202 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 145 —-Connections of elec¬ 
tromagnetic regulator to main¬ 
tain constant current. The 
winding M is of large wire and 
is connected in series with the 
generator and battery 



Fig. 14 <>—Connections of elec¬ 
tromagnetic regulator to main¬ 
tain constant voltage. The 
winding M has more turns and 
is connected directly to the 
terminals of the generator 


winding M, decreasing in value, and the magnetic pull of the cor* 
of the electromagnet is no longer sufficient to overcome the pull 
of the spring S, so the armature moves away from the core and 
t hf> eontact C is closed. The closing of the contact C short-circuits 















































































REGULATION OF GENERATOR OUTPUT 203 

the resistance R, and the field current starts to build up. At 
the same time the magnetic field in which the armature is revolv¬ 
ing increases, which results in an increase in the generated elec¬ 
trical pressure in the armature and, hence, an increase in the cur¬ 
rent in the winding M. The armature A again is drawn over 
toward the core of the electromagnet, breaking the contact C 
and reintroducing the resistance R in the field circuit. This 
operation is repeated over and over hundreds of times a minute, 
and the current delivered by the generator, which passes through 
the winding M, is maintained practically constant at a value de¬ 
pending upon the adjustment of the spring S and the length of 
the air gap between the armature and the end of the core of the 
electromagnet. The stronger the spring S and the larger the air 
gap, the greater the value of the current in the winding M 
must be in order that the armature be drawn toward the core of 
the electromagnet and the contact C broken. Likewise, the 
weaker the spring S and the shorter the air gap, the less current 
required in the winding M to repeat the above operation. 

A slight variation in the winding of the electromagnet and its 
connections may be made as shown in Fig. 146, when it is desired 
to maintain a constant voltage at the terminals of the generator 
rather than a constant current, independent of the speed of the 
generator armature. The only difference is that the winding M 
of the electromagnet is composed of a relatively large number of 
turns of much smaller wire and this winding is connected directly 
to the terminals of the generator rather than in series with the 
generator and battery as in Fig. 145. The current in the winding 
M will increase and decrease with generator voltage, and when 
the voltage is high enough to produce sufficient current in the 
winding so that the magnetic pull on the armature A will over¬ 
come the action of the spring S, the contact C will be broken and 
the resistance R introduced in series with the field winding. The 
action of the resistance R is exactly the same as in Fig. 145, and 
when the electrical pressure has decreased to such a value that 
the current it is capable of producing in the winding M does 
not produce sufficient magnetic pull on the armature to overcome 
the action of the spring S, the armature will move away from the 
core and the contact C will be closed, thus short-circuiting the 
resistance R. 

The voltage of the generator builds up again until the magnetic 


204 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


pull due to the current in M overcomes the action of the spring S, 
etc. This operation is repeated hundreds of times each minute, 
and Hie voltage of the generator remains practically constant. 
The value of the voltage the generator will maintain will depend 
upon the length of the air gap between the armature and the 
core of the electromagnet and also the tension on the spring S. 



The greater the length of the air gap and the stronger the tension 
in the spring the greater the value of the voltage the generator 
will maintain, as a larger current will be required in the winding 
M to attract the armature and this larger current will be produced 
only when the voltage increases, as the resistance of the winding 
is practically constant. Likewise, a decrease in the length of 
the air gap and the weaker the spring, the lower the value of the 
Voltage the generator will maintain. 

This principle of operation has been used by the Delco, Gray & 
Davis, North East, Ward Leonard, Remy, Simms-Huff and Allis- 
Chalmers. 

Systems having electromagnetic types of regulators nearly al¬ 
ways have an electromagnetic cutout. The two are usually com¬ 
bined in one housing, or containing case, and the combination is 












































REGULATION OF GENERATOR OUTPUT 


205 


spoken of as a controller. In some cases a single electromagnet 
with two windings will be used, while in some cases two electro¬ 
magnets will be used, one for the regulator and one for the cut¬ 
out. The connection of a controller with a single electromagnet 
is shown diagrammatically in Fig. 147. The electromagnet is so 
arranged that the left-hand armature Ai will be attracted when 
the current in the winding Mi produces sufficient magnetic pull 
on the armatures to overcome the action of the spring Si. When 
the armature Ai is drawn over toward the core of the electro¬ 
magnet, the contact Ci is closed and the generator and battery 
are connected in series, and the generator starts to charge the 
battery, the current passing through the winding M 2 on the elec¬ 
tro-magnet. As the current in the winding M 2 increases, due 
to any cause, there will be an increase in magnetic pull on the 
armature A , and when this pull is sufficient to overcome the 
action of the spring S 2 the armature A 2 will be drawn over to 
the left and the contact C 2 broken. The resistance R causes the 
current in the field winding to decrease, and, hence, there is a 
decrease in generated voltage and also a decrease in the value of 
the current in windings M g and M^. 

When the magnetic action of the currents in windings Mi and 
M 2 have decreased to such an extent that the armature A 2 is 
drawn away by the action of the spring S 2 , the resistance R is 
short-circuited and the voltage starts to build up again, thus in¬ 
creasing the current in the windings. When the voltage decreases 
below that required to charge the battery, assuming the adjust¬ 
ment of the spring Si and the length of the air gap between the 
armature Ai and the core of the electromagnet are correct, the 
magnetic pull due to the current in the winding M x is no longer 
sufficient to overcome the action of the spring Si and the contact 
Ci is broken, and the generator and battery are no longer con¬ 
nected in series. The magnetic pull required to overcome the 
action of the spring Si is less than that required to overcome 
the action of the spring S 2 , which accounts for the armature A x 
being drawn over before the armature A 2 . When the generator 
is charging the battery, the currents in the windings M x and M 2 
pass around the core of the electromagnet in the same direction, 
but if the battery should start to discharge into the generator 
for any reason the magnetic action of the current in the winding 
M 2 will oppose the magnetic action in M x and the armature A t 
will move away from the core, breaking the contact Cj. 


206 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The wiring diagram of the combined regulator and cutout of 
the Allis-Chalmers Co. is shown in Fig. 148. In this ease a single 
electromagnet with two windings is used. One of these windings, 
the shunt, serves the purpose of a cutout, while the other, the 
series, regulates the value of the charging current. When the 
generator voltage is sufficient to charge the battery, the magnetic 
action of the current in the shunt winding attracts the armature 
carrying the cutout contact and the battery starts to charge, the 



Fig. 148 —Wiring diagram of Al lis-Chalmers combined regulator 
and cutout. A single electrom agnet with two windings is used 


current in the series coil assisting the current in the shunt coil 
in holding the armature in place. If the charging current in¬ 
creases, due to any cause such as an increase in the speed of the 
generator, the magnetic pull on the second armature will increase 
and at some particular value of charging current the second arma¬ 
ture will start to vibrate. The vibration of the second armature 
will cut in and out a resistance in the field of the generator, which 
will cause a reduction in the charging current by lowering the 
voltage of the generator. 

















































REGULATION OF GENERATOR OUTPUT 


207 


Inserting Resistance in Field Circuit Intermittently By Means 
of a Magnetic Vibrator in Combination With a Load Control: 
The wiring diagram of the Remy controller shown in Fig. 149 
illustrates the use of a magnetic vibrator that is influenced by 
the lamp load in such a manner that the output of the generator 
is automatically increased whenever the lamps are lighted and the 
engine is running at a speed high enough to charge the battery. 
The cutout has a series winding Mj^ and a shunt winding M 2 . 
As the voltage of the machine builds up, the current in the wind¬ 
ing M 2 increases until there is sufficient magnetic pull on the 
armature A^ to draw it over against the action of the spring Si 
and close the contact Ci. The contact Ci completes the circuit 
beween the generator and the battery, and the battery starts 
to charge, the current passing through the series winding M 2 and 
the winding M 3 on the second electromagnet. When this current 
exceeds a certain value the armature A 2 is drawn over by the 
magnetic pull and the contacts at C 2 are broken and the resistances 
Rl and R 2 introduced in series with the field windings. The 
field current decreases in value, and, hence, the generated voltage 
which causes a decrease in the value of the charging current in¬ 
creases. As the charging current decreases in value the magnetic 
pull on the armature A 2 decreases, and finally the spring pulls 
the armature away from the core of the electromagnet and the 
contacts at C 2 are closed. The closing of the contacts at C 2 short- 
circuits the resistances Ri and R^- The voltage of the generator 
then starts to build up, and the above cycle of operations is 
repeated many hundred times a minute. 

A connection is made to the winding M 3 at the point D, as 
shown in the figure, and the current for the lamps passes through 
only a portion of the winding M 3 . The current delivered by the 
generator with the lamps turned on will be greater than when the 
lamps are turned off, for the following reason: When the lamps 
are turned on the magnetic pull on the armature A 3 is due to the 
magnetic action of the charging current going to the battery and 
passing through the entire winding M 3 plus the magnetic action 
of the lamp current passing through the part of the winding 

M 3 from the left-hand end to the point D. It is obvious that the 

total magnetic action of these two currents will be less than the 

magnetic action of a current equal to the sum of the two and 

passing through the entire winding. Hence, since the magnetic 
uction on the armature A 2 is to be the same when the tension of 


208 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

snu/nriELD imm coil 



generator output increases 
when the lamps are lighted 
and the engine is charging the 
battery 


a vibrating magnet in combi¬ 
nation with a bucking coil. 
Such regulation is seldom en¬ 
countered y however 


the spring S 2 is overcome, no matter whether the lamps be turned 
on or not, the sum of the lamp current and the current to the 
battery will be greater than the current to the battery when the 
lamps are turned off. 






































































































REGULATION OF GENERATOR OUTPUT 


209 


Energizing the Bucking Coil Intermittently by Means of a Mag¬ 
netic Vibrator: A system of regulation, that is very seldom en¬ 
countered, makes use of a vibrating magnet, similar to those pre¬ 
viously described, in combination with a bucking coil. The prin¬ 
ciple of operation of such a system can be easily understood by 
reference to Fig. 150. The resistance R in Fig. 145 has been re¬ 
placed by an additional field winding, which carries a current when 
the contact C is open. The direction of the current in the buck¬ 
ing coil is such as to produce a magnetizing effect in the opposite 
direction to that produced by the current in the main or shunt 
field winding. Some systems have made use of the bucking coil 
in parallel with the resistance, and only a part of the shunt field 
current passes through the bucking coil. 

Electromagnet Used in Combination with a Carbon Field 
Resistance: The carbon used in the construction of field re¬ 

sistances is in two forms. One form consists of a large number 
of small carbon discs piled on top of each other and normally 
held together tightly under the tension of a spring, so that ^iieir 
resistance is quite low. The armature of the regulator is attached 
to the spring so the magnetic pull on the armature lessens the 
tension of the spring holding the carbon discs together and the 
resistance of the combination is increased, due to the fact that 
the various discs are making poorer contact with each other than 
they were when the tension of the spring holding them together 
was at its maximum value. The magnetic pull on the armature 
of the electromagnet will depend on the value of the current in 
the winding, which may be arranged to vary as the current from 
the generator by connecting the winding in series with the gen¬ 
erator, or as the voltage of the generator by connecting the wind¬ 
ing to the terminals of the generator. In the first case the wind¬ 
ing will consist of a small number of turns of large wire, while 
in the second case the winding will consist of a relatively large 
number of turns of small wire. Carbon resistances composed of 
discs have been used in some models of the U. S. L. and Aplco 
equipment. 

The other form of carbon used in the construction of field resist¬ 
ances is finely divided, or powdered, carbon in combination with 
small flakes of mica. This mixture of carbon and mica is carried 
in a suitable cup, or cylinder, and is compressed by a plunger 
which normally is held against the mixture under the action of 


210 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

a spring. The action of the spring is counteracted to varying 
degrees by the magnetic pull of an electromagnet, and the pres¬ 
sure of the plunger against the mixture of carbon is varied. The 
small particles of mica give to the mixture a springiness which 
causes the particles of carbon to separate to a certain extent 
when the pressure is reduced and as a result increases the re¬ 
sistance of the mixture. A good example of this type of carbon 
resistance is found in the voltage regulator of the Bosch com¬ 
pany. 

The operation of the U. S. L. regulator that has the carbon- 
disc resistance may be understood readily by reference to Fig. 
151, which gives a wiring diagram of the connections. In this 
system two storage batteries are used. They are charged in par¬ 
allel and discharged in series through the starting motor, the 
change in connections being made by the starting switch. The 
connections in the starting switch for both the generating and 
starting positions are shown. The circuits through the regulator 
may be traced as follows: Starting with the generator terminal 
marked A+, which corresponds to the positive set of brushes, 
go to the contact G-f- of the touring switch and then to the ter¬ 
minal A+ on the controller. From the terminal A+ on the con¬ 
troller you may return to the negative set of brushes on the gen¬ 
erator by two circuits. One of these circuits is from A+ on the 
controller through the lower coil, called the shunt winding in this 
case, to the terminal B2-; thence to the terminal B2- on the 
starting switch; thence from A- on the starting switch to A- on 
the generator; thence through the series winding on the fields to 
the negative set of brushes, and then through the armature 
winding back to the starting point, or generator terminal A+. 
The second circuit between the terminal A-j- on the controller 
and the negative set of brushes on the generator is through the 
carbon resistance indicated at the top of the regulator to the 
terminal F+; thence through the r shunt field winding to the 
junction of the shunt and series field windings, which corresponds 
to the negative set of brushes on the generator; and then 
through the armature winding back to the starting point, or gen¬ 
erator terminal A-f-. 

As the voltage of the generator builds up, due to increase in 
speed and field strength, the current in the shunt winding on the 
controller, which is connected between the terminals A+ and 


REGULATION OF GENERATOR OUTPUT 


211 


B2-, increases in value. When the magnetic pull due to the cur¬ 
rent in the shunt winding reaches a certain value, an armature 
of the electromagnet is drawn over and the contacts between 
the terminals A+ and B2+ on the controller are closed. The 


1—OKI 

•ito- 

mn 

MW 


> < 

r ' < 



CONTROLLER 


AMMETER 


TOM 

SWITCH 



STARTING 1 SWITCH 
STARTING fOSITIOJf 


Fig. 151 —This wiring diagram shows the connections of the 
U. 8. L. regulator and cutout. The field resistance is in the 
carbon disc form 

closing of these contacts completes a cir uit between the positive 
and negative terminals of the generator through the batteries. 
This circuit may be traced as follows: From A+ on the gener¬ 
ator through the contacts G+ on the touring switch to the ter- 























































































2-12 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


rainal A-f- on the controller; thence through the series winding 
and contacts to the terminal B2+ on the controller; thence 
through the ammeter to the contacts B+ on the touring switch. 

From the right-hand contact, marked B+, on the touring switch, 
the circuit divides, one going directly to the terminal B2+ of 
the upper battery through the battery to the terminal B2-, and 
then to the negative terminal of the generator. The second cir¬ 
cuit goes to B2+ on the starting switch; thence to B1 + on 
starting switch; thence to the terminal B1 + of the lower bat¬ 
tery through the battery to the terminal B1-, and thence to the 
negative terminal of the generator. When the above connections 
are made the generator is charging the two batteries in parallel 
and the ammeter is indicating the sum of the currents in the two 
batteries, assuming no lights are turned on. The current in the 
series coil of the controller is the same as that indicated by the 
ammeter. When the current in this series coil exceeds a certain 
value the magnetic action of the current causes sufficient pull on 
an armature to partially overcome the action of the adjusting 
spring, and the force holding the carbon discs together is re¬ 
duced, causing an increase in the resistance they offer. Hence, 
the value of the field current and the value of the voltage gen¬ 
erated will decrease. A description of the operation of the re¬ 
mainder of this system will be given later. The complete con¬ 
troller with the cover removed is shown in Fig. 152, and the more 
important parts are marked. The indicator gives a visible indi¬ 
cation as to whether the cutout is operating or not, the end of 
the pointer showing through a small hole in the top of the cover. 

Electromagnet Used in Opening the Field Circuit of the Gen¬ 
erator: The Aplco systems make use of an electromagnet whose 
winding is connected directly to the terminals of the battery. The 
armature of this electromagnet controls a set of contacts which 
normally are closed and connected in series with the field wind¬ 
ing of the generator. When the voltage of the battery has 
reached a value ample to produce current in the winding of the 
electromagnet so that the magnetic pull on the armature over¬ 
comes the tension on the adjusting spring, the contacts open and 
the current in the field winding is reduced to zero value. This 
is neglecting the effect of residual magnetism. The battery will 
not be charged until its voltage drops to a certain value, depend¬ 
ing on th« adjustment of the spring controlling the armature on 


REGULATION OF GENERATOR OUTPUT 213 

which the contacts are mounted. This will allow the contacts 
in the field circuit to close again. 

Varying the Value of the Field Resistance by a Solenoid: The 
Adlake equipment has a regulator which consists of a resistance 
whose value is controlled by the magnetic action of a solenoid. 
The device, in brief, consists of an arm pivoted at one end and 
equipped with a carbon brush on the other end. This carbon 
brush moves over a number of metal segments arranged in the 
form of an arc of a circle and connected together by a small coil 
of resistance wire. The field circuit of the generator has one 
terminal connected to the arm and another connected to one 
end of the series of segments. The position of the carbon brush 
on the segments will determine the portion of the total resistance 
connected in series with the field winding. For example, when 



CARBON PILE LEVER AIR CAP 
. . . * 


INDICATOR 


CHARGING CONTACTS 

SWITCH LEVER- 

MAGNET COIL _ 

.SWITCH LEVERS PR INC? 


THRUST PLATE 

PILE LEVER 
UPPER ADJUSTING PLUG 


ADJUSTMENT CLAMPING 
SCREWS 


LOWER ADJUSTING PLUG 


Fig. 152 —The cover of the U. S. L. regulator and cutout has been 
removed, and the more important parts are marked. The indi¬ 
cator acts as a barometer for the cutout 


the carbon brush is on the segment to which the field winding is 
connected, no part of the resistance will be in series with the 
field; on the other hand, if the carbon brush is on the segment 
farthest removed from the one to which the field winding is con¬ 
nected, all the resistance will be in series with the field wind¬ 
ing. The normal position of the arm corresponds to the one in 
which there is no part of the resistance in series with the field 
winding. The position of the rheostat arm is determined by the 
combined magnetic action of the current in the winding of the 
solenoid about the iron core marked T, Fig. 153, and the weight 
of the plunger R, the core and plunger being attached to the 





214 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

opposite ends of a short cable which passes over a grooved wheel 
attached to the rheostat arm. The weight of the plunger R may 
be increased by adding more shot and decreased by removing 
some of the shot. Increasing the weight of the plunger R will 
increase the current required to produce a given movement of the 
rheostat arm. 

The entire output of the generator passes through the winding 

of the solenoid, and as this cur¬ 
rent output tends to exceed the 
value for which the adjustment 
has been made the iron core 
marked T will be drawn into 
the solenoid, causing the carbon 
brush on the end of the rheostat 
arm to move down over the seg¬ 
ments. The value of the resist¬ 
ance in the field circuit will be 
increased, causing a decrease in 
the value of the field current 
and, hence, a decrease in the 
electrical pressure in the arma¬ 
ture of the generator. 

A wiring diagram of the Ad- 
lake-Newbold combined regula¬ 
tor and cutout is shown in Fig. 

153. The complete device, with 
cover removed, is shown in Fig. 

154. The generator is of the 
shunt-wound type and the field 
circuit may be traced as follows: 
Starting with the generator 
terminal marked +D, go to 
the corresponding terminal on 

the controller marked +D; thence to the fuse clip marked 6; 
thence to the terminal of the rheostat marked 3; thence through 
the resistance coils to the carbon brush on the end of the rheostat 
arm; thence to the screw 19; thence through the flexible connec¬ 
tion to the screw 18; thence to the fuse clip marked 2; thence 
through the fuse 5 to the clip 1; thence to the terminal +F on the 
regulator; thence to the corresponding terminal on the generator 



HEAD LAMP SWITCH 
/ HEADIMS 

tCH 


/■> 5JDE 
M LAMBS 

id 


.'I'H 

MTTERY 
TAIL LAMP— 0 
'DYNAMO 

Fig. 153 —A solenoid controls 
the value of the field resist¬ 
ance in this Adlake-Newhold 
regulator and cutout 














































REGULATION OF GENERATOR OUTPUT 215 

marked +F; thence through the shunt field winding to the ter¬ 
minal of the generator -D; thence through the armature winding 
to the starting point +D. 

A second circuit exists between the terminals +D and -D of 
the generator, even though the contacts of the cutout be open. 
It may be traced as follows: Starting with the terminal +D; 
thence to the fuse clip 6; thence through the fuse 10 to clip 7; 
thence through a winding on the solenoid to the connecting ter¬ 
minal 20; thence to the point X 
on the stationary contact of the 
cutout; thence through the 
windings of the two upper elec¬ 
tromagnets in series to the con¬ 
necting terminal 15, and then to 
the terminal -D on the generator. 

As the voltage of the genera¬ 
tor builds up, the current in the 
circuit just traced through in¬ 
creases, and when the magnetic 
pull produced by the current in 
the two upper electromagnets i^ 
sufficient to draw up the two 
lower electronThgnets, which are 
mounted on the piece of iron Z, 
the cutout contacts at W1 and 
W2 will be closed. The closing 
of the cutout contacts will com¬ 
plete a new circuit which may 
be traced as follows: Starting 
with the generator terminal -f D; 
thence through fuse 10; thence 
through a winding on the solenoid to the connecting terminal 20; 
thence to the point X and to the upper, or stationary, cutout con¬ 
tact Wl; thence to the lower cutout contact W2; thence through 
the windings of the two lower electromagnets in series to the con¬ 
necting terminal 14; thence to the controller terminal +B; thence 
to the positive terminal of the battery marked +B through the 
battery to the terminal -B; thence to the negative terminal of 
the generator, and thence through the armature winding to the 
terminal +D, or starting point. 



Fig. 154 —This shows the Ad- 
lake-Neichold device with the 
cover removed. The generator 
is a shunt wound type 







216 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

In tracing this last circuit, the lamps were assumed to be 
turned off. The current in the two lower electromagnets assists 
in holding the cutout contacts closed as long as the battery is 
charging, but should the battery start to discharge the magnetic 
action will be opposite that produced by the upper electromagnets 
and the cutout contacts will open. The front lamps take their 
current through a special switch, whose connections are such that 
the resultant magnetic action of the generator current in the 
solenoid is less with the front lamps on than without them. Hence 
the current output of the generator is increased when these lamps 
are turned on. The switch in the upper left-hand corner, marked 
N in Fig. 153, is for getting the night rate of current output from 
the generator continuously should conditions demand it. 

Solenoid and 11 Mercury Well’’ Control of Field Resistance: A 
number of the earlier Delco systems were equipped with a regu¬ 
lator known as the mercury well type. A cross-section of one is 
shown in Fig. 155. This regulator consists of a winding, A, which 
surrounds the upper end of a mercury tube, B. Inside this mer¬ 
cury tube is a plunger tube, C, with a winding of resistance wire, 
R, about its lower end. One end of the winding R is attached to 
the cover end of the plunger tube and the other end is connected 
to a needle, N, carried in the center of the lower end of the tube. 
The lower portion of the mercury tube is divided by'an insulating 
tube into two concentric compartments, the plunger tube being 
partly immersed in the outer compartment and the lower end of 
the needle N in the inner compartment. The space in the mer¬ 
cury tube above the mercury is filled with a special kind of oil, 
which serves the double purpose of protecting the mercury from 
oxidization and of lubricating the plunger tube. The whole 
device is supported by a bracket, D. 

The terminals of the winding A are connected to the two wires 
leading from the generator brushes, and as the voltage of the 
generator increases the current in the winding increases. Hence, 
there is an increase in the magnetic pull on the iron plunger 
tube C. As the lower end of the plunger tube is withdrawn from 
the mercury, due to the magnetic pull of the winding A, more 
resistance is inserted in series with the shunt field winding of 
the generator, as the field current must now pass through a greater 
length of the wire in the winding R in passing from the needle 
N to the mercury in the outside mercury well. With this increase 


REGULATION OF GENERATOR OUTPUT 217 

in resistance in the field winding there is a smaller field current 
for a given terminal voltage. Hence, the terminal voltage of the 
generator does not increase as rapidly as it would if no resistance 
were inserted in series with the 
field winding. As the charging of 
the battery continues the voltage 
of the system increases, and the 
magnetic pull produced by the 
winding A increases, causing more 
resistance to be inserted in the field 
circuit and thus preventing an ex¬ 
cessive charging current while the 
battery is approaching a condition 
of complete discharge. With a de¬ 
crease in speed of the generator, 
there will be a decrease in the gen¬ 
erated voltage, thus causing a de¬ 
crease in the magnetic pull pro¬ 
duced by the current in the winding 
A and, hence, a decrease in the re¬ 
sistance of the field circuit, whieh 
prevents the voltage decreasing as 
rapidly as it would otherwise. 

A variable resistance, E, is con¬ 
nected in the supporting bracket D 
and connected in series with the 
winding H. The value of the por¬ 
tion of this resistance in series with 
A may be adjusted at any time by a 
lever, F. The object of this adjust¬ 
ment is to take care of the varia¬ 
tions in the battery voltage, due to 
changes in temperature. 

An Electromagnet Used in Con¬ 
trolling the Connections of the 
Field Circuits: In some of the old¬ 
er types of Delco equipment an 
electromagnet was used to change 

the connections of the field windings and to regulate the out¬ 
put of the generator as follows: The field of the generator 



Fig . 155 —A cross-sectton of 
the mercury well regulator. 
Some of the earlier Delco sys¬ 
tems used this type 





































































218 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

is produced by permanent magnets which are provided with 
several shunt field windings. The connections of these shunt 
field windings are controlled by the electromagnet, whose mag¬ 
net action is governed by the output of the generator. At low 
engine speeds the shunt fields are connected so that they as¬ 
sist the permanent magnets in producing a magnetic field for 
the armature to revolve in. With an increase in voltage of 
the generator, due to an increase in speed, the field windings 
are disconnected, the permanent magnets act alone to produce 
the magnetic field and the increase in voltage is not as great 
as it would be had the shunt field windings remained con¬ 
nected. With a still further increase in voltage the shunt field 



Fig. 156 —A slipping clutch operates this Gray & Davis generator 


windings are again connected with a resistance in series, but in 
such a manner that the current in them produces a magnetic 
effect opposite to that produced by the permanent magnets and 
the field strength is reduced, which counteracts to a certain ex¬ 
tent the increase in speed. The resistance in series with the 
field winding is removed by a change in connections when the 
voltage reaches a value produced by the highest engine speeds 
and the maximum magnetizing action of the shunt fields oppose 
the permanent magnets. 

Mechanical Regulation 

Generator Operated at a Constant Speed by a Slipping Clutch 
Controlled by a Centrifugal Governor: If a shunt generator be 
operated at a constant speed, the voltage will build up to a 
definite value and remain practically constant. The value of this 












































































REGULATION OF GENERATOR OUTPUT 219 

definite voltage can be adjusted by charging the value of tho 
resistance of the shunt field winding and, unless there is a change 
in the speed or resistance of the field, will remain practically con¬ 
stant so long as there is no change in the value of the current 
the generator is delivering. The regulation of a number of dif¬ 
ferent systems put on the market by the Gray & Davis Co. is 
accomplished in this manner. In the systems a series field wind¬ 
ing usually is provided. This series field is arranged to carry 
all or a certain part of the current delivered by the generator, 
and its magnetizing action assists the magnetizing action of the 
shunt field and causes an increase in the value of the field strength 
with an increase in current delivered and, hence, an increase in 
generated voltage with an increase in the current output. The 
magnetizing action of this series 
field is usually adjusted so that 
the increase in generated volt¬ 
age is just enough to counteract 
any loss in the armature and 
connecting leads, due to the in¬ 
creased output which results in 
the voltage at the terminals re¬ 
maining fairly constant for all 
loads. The cross-section of a 
generator of this type made by 
the Gray & Davis Co. is shown 
in Fig. 156, and the operation 
of the driving clutch will be 
apparent after a careful inspec¬ 
tion of the figure. 

A friction clutch used by the Auto-Lite Co. in some of their 
earlier equipments for operating the generator at a constant speed 
is shown in Fig. 157. The governor consists of a drum, D, fastened 
to the driving shaft and of two friction shoes, B, each being 
attached to a weight, W, and normally held against the inside 
surface of the drum by the action of coiled springs placed in 
the ends of the arm A. As the speed at which the arm A rotates 
increases there is a tendency for the weights W to be thrown 
outward from the point about which they rotate. The two arms 
carrying the weights are pivoted at the ends of the arm A, and 
as the weights are thrown outward the action of the springs hold- 



Fig. 157 —This Auto-Lite fric¬ 
tion clutch also tends to main¬ 
tain a constant speed 



220 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ing the friction shoes against the cylinder is decreased. The 
speed at which the clutch slips may be changed by moving the 
weights W toward or away from the points at which the arms 
carrying them are pivoted. The nearer the weights are to these 
points the higher the speed necessary for the clutch to slip 
and likewise, the farther these weights are away from these points 
the lower the speed necessary for the clutch to slip. 

Centrifugal Governor Used in Inserting Resistance in the 
Charging Circuit: A good example of this type of regulation is 
found in a machine manufactured by the Vesta Co. In this ma¬ 
chine the position of a rheostat arm on the contact segments of 
a small rheostat is controlled by the action of a centrifugal gov¬ 
ernor. The end contact of the rheostat, on which the end of 
the rheostat arms rests normally and at low engine speeds, is 
not electrically connected to any of the other circuits. The 
charging circuit for the battery is connected to the rheostat arm, 
and when the end of the arm is on this insulated segment the 
electrical connection between the generator and the battery is 
not complete. The end of the arm travels over the contact seg¬ 
ments of the rheostat with an increase in speed, and when it 
comes in contact with the second point the circuit connecting 
the generator and battery is closed. A further movement of 
the arm inserts resistance in series with the generator and bat¬ 
tery and thus prevents an excessive charging current. 

Regulation by Ampere-Hour Meter 

Some of the earlier Delco systems made use of an ampere- 
hour meter that measured the quantity of electricity put into 
and taken out of the battery and gave an indication of these 
quantities on a suitable dial. The pointer on the indicating dial 
of this instrument travels in one direction when the battery is 
charging and in the opposite direction when the battery is dis¬ 
charging. The difference in the indications of this pointer at two 
different times is a measure of the net quantity of electricity 
put in or drawn from the battery during the interval between 
taking the two readings. A double set of contacts is carried in 
the containing case of the instrument, through which the field 
current of the generator must pass. A movement of the pointer 
of the meter past a certain position causes one set of these con¬ 
tacts to open and, with further movement past this point in 
the same direction, causes the second set of contacts to separate 


REGULATION OF GENERATOR OUTPUT 221 

When the first set of contacts is opened a resistance is inserted 
in series with the field and the charging current is reduced. 
When the second set of contacts opens the field circuit is opened 
altogether, and the charging of the battery is practically stopped, 
as there is no field, except that due to residual magnetism, for 
the armature of the generator to revolve in. The reverse opera¬ 
tion of these contacts takes place when the battery discharges 
and the pointer is turned in the opposite direction. With this 
system the rate at which the battery is charged is governed by 
the amount of charge in the battery. The hand on the meter 
must be moved in the direction of charge at certain intervals, 
because there must always be a greater number of ampere-hours 
put into the battery than it can supply. The meter hand is 
mounted in such a way that this adjustment easily may be made. 

Suggestions in Adjustment of Regulators 

The adjustment of the regulator equipment on the different cars 
is made by the manufacturers of the equipment or at the factory 
where the equipment is installed and is correct for that par¬ 
ticular make and model of car under ordinary conditions. Under 
no conditions should this adjustment be changed unless the per¬ 
son making the change is positive that such a change is required, 
and even then it is best to have an experienced man make the 
adjustment, as more damage may be done than good. Difficulties 
arising from improper change in the adjustment of the regu¬ 
lator may not be apparent at the time the change is made, and 
the car may run for a considerable period before there is definite 
evidence of the difficulty. In the majority of cases low genera¬ 
tor output is due to improper care of the commutator and brushes, 
in not keeping all the various electrical connections clean and 
tight or in not giving the battery the necessary attention. 

Occasionally unusual conditions may arise in the operation of 
the car, which will demand an increase in the generator output. 
For example, the addition of extra electrical equipment may 
necessitate an increase in the rate at which the battery is 
charged for a given speed of the car. It is always advisable to 
make sure that you are not demanding a larger output from the 
battery than it is capable of handling under ordinary conditions, 
as permanent damage to the electrical equipment will be the ulti¬ 
mate result. In some cases a car may be driven a great deal 
more at night than in the daytime, and with the lamps lighted 


222 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


the demands on the battery will be increased. Under these condi¬ 
tions it is necessary to increase the rate at which the generator 
will charge the battery for a given engine speed. Owing to the 
lower efficiency of the battery in the winter and the greater use 
of the lamps, the charging rate of the generator should, as a rule, 
be increased. It may be advisable to lower the charging rate 
of the generator or to stop the charging operation altogether on 
a long drive, by disconnecting the generator, short-circuiting it 
or removing the field fuse, depending on the kind of generator 
and the method of regulating its output. In some cases a special 
switch, called the touring switch, is provided. This produces the 
necessary changes in connection, when it is turned to the proper 
position, which causes a reduction in generator output. 


CHAPTER XVI 

Electric Motors 


Principle of the Direct-Current Motor 

I F a wire in which there is a direct current be placed in a mag¬ 
netic field in such a position that the center of the wire does 
not correspond in position to the direction of the magnetic field, 
a force will act on the wire, due to the action of the current 
in the wire and the magnetic field on each other. This force is 
present in the generator when the machine is operating and there 
is a current in the armature, and it tends to cause the armature 
to revolve in the opposite direction to that in which the gasoline 
engine is rotating the armature. If the strength of the magnetic 
field or the value of the current in the wire increases, the position 
of the two with respect to each other remaining constant, the 
force tending to move them with respect to each other will 
increase. The value of the force between the magnetic field and 
the wire depends on their relative positions; it is at its maximum 
when the center of the wire and the direction of the magnetic 
field are at right angles to each other, and at its minimum when 
the center of the wire and the direction of the magnetic field are 
parallel to each other. 

The production of the force acting on the conductor may be 
explained as follows: A conductor, W, carrying a current away 
from the observer and placed in a magnetic field, H, whose direc¬ 
tion is from the left toward the right is shown in Fig. 158. The 
current in the conductor tends to produce a magnetic field about 
the conductor in a clockwise direction, which results in the main 
magnetic field being strengthened on the upper side of the con¬ 
ductor, where the two fields are in the same direction, and weak¬ 
ened on the lower side of the conductor, where the two fields are 
in opposite directions. As previously explained two magnetic 
fields cannot exist in the same space at the same time but combine 


224 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

to form a resultant magnetic field. Since the magnetic field is 
so much stronger on the upper side of the conductor than on 
the lower side, the conductor is acted on by a force, F, which 
tends to move it down or toward the bottom of the field 

The Left-Hand, or Motor, Rule 

A definite relation exists between the direction of the current 
in a wire placed in a magnetic field, the direction of the magnetic 


> 






vjr 

Fig. 158 —The force acting on a conductor in which there is a 
current tends to move it up or down, depending upon the direc¬ 
tion of the current and the direction of the magnetic field, when 
the conductor is placed in a magnetic field 


field and the direction of the force tending to move the wire 
with respect to the magnetic field. If the thumb and first and 
second fingers of the left hand be placed at right angles to each 
other, Fig. 159, the second finger pointing in the direction of the 
current in the conductor and the first finger in the direction of 
the magnetic field, then the thumb will point in the direction in 
which the conductor will tend to move. This simple rule is known 
as the left-hand, or motor, rule. If the direction of current in the 
wire be reversed, the direction of the magnetic field remaining 
constant, the direction of the force acting on the conductor will 











ELECTRIC MOTORS 


225 


be reversed; or, if the direction of the magnetic field be reversed, 
the direction of current in the wire remaining the same, the 
direction of the force on the wire will be reversed. If, however, 
the direction of the current in the wire and the direction of the 
magnetic field are both reversed, the direction of the force on the 
wire will remain the same. 

Generator and Motor Interchangeable 

The essential parts of a direct-current motor are identical 
with those of a generator, namely, an armature and a magnetic 
field. The connection of the wires on the surface of the arma- 



Fig. 159 —The left-hand, or motor, rule is used to determine the 
direction of the conductor’s movement when the directions of the 
conductor's current and the magnetic field are known 

ture to the external circuit is made by a commutator, which 
serves to reverse the current in the various parts of the arma¬ 
ture winding at the proper time, so that the force acting on the 
various wires tends to produce rotation in the same direction, 
and, as a result, continuous rotation of the armature is produced. 
Any direct-current generator may be used as a direct-current 







220 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

motor, or vice versa, their construction being practically the 
same. 

Simple Experiment Illustrating Fundamental Principle of the 
Direct-Current Motor and Right-Hand Rule: A simple experi¬ 
ment may be arranged to verify the facts stated in the two 



Fig. 100 —This simple experiment illustrates the fundamental prin¬ 
ciples of the direct-current motor and the right-hand rule 

previous sections, Fig. 160, which consists of a U-shaped piece 
of copper wire supported by two metal supports forked at their 
upper end so that the wire is free to turn and at the same time 
makes good electrical contact with the supports. The lower 
ends of the supports are connected to two binding posts as in 
the figure. A strong permanent magnet, M, is placed with its 






































ELECTRIC MOTORS 


227 


poles on opposite sides of the wire as indicated in the figure. 
If a current be sent through the wire, the wire will deflect from 
its normal position. The degree of this deflection will depend 
on the value of the current, and the direction of the deflection 
will depend on the direction of the current in relation to the 
direction of the magnetic field. When the north pole of the 
magnet is on the upper side and the current in the wire is in 
the direction indicated in the figure, the deflection or movement 
of the wire will be toward the left. If the magnet be turned 



Fig. 161 —In the operation of this two-part commutator the direc¬ 
tion of the force acting on any part of the coil can be determined 


by application of the left-hand rule 

over, that is, if the field be reversed, the direction of the deflec¬ 
tion will be reversed, or if the current be reversed, the direction 
of the deflection will be reversed. The direction of the deflection 
will remain unchanged when the direction of the field and the 
direction of the current are reversed at the same time. 

Operation of Two-Part Commutator 

If a single loop of wire be mounted on an axis which is at 
right angles to the direction of a magnetic field, Fig. 161, and a 
current be supplied to the coil by means of a two-part commuta¬ 
tor and two brushes which rest on the commutator exactly oppo¬ 
site each other, a force will act on the sides and ends of the coil. 
The direction of the force acting on any part of the coil may 
be determined for all the different positions the coil may occupy 
when it turns on the axis supporting it by a simple application o t 

























228 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the left-hand, or motor, rule. Remember that the force acting 
on the conductor is always perpendicular to the direction of the 
magnetic field; then proceed to investigate the force acting on 
the coil for various positions. The resultant force which tends 
to produce rotation acting on the two ends of the coil will be 
zero for all positions of the coil. The forces acting on the two 
sides of the coil will be equal in value for all positions, but the 
directions of the forces on the two sides will be exactly oppo¬ 
site each other. If the force on one side tends to move that side 



Fig. 162 —When the coil is in a horizontal position, as shown by 
this cross-section, the effect of the forces tending to produce rota¬ 
tion is at a maximum 

of the coil up, then the force on tbe other side tends to move 
that side down. The force acting on one side will always be 
up and the force on the other side will always be down, and both 
will remain constant in value as long as there is DO change in the 
strength of the magnetic field or in the value of the current. 

These forces on opposite sides of the coil, being in opposite 
directions, tend to rotate the coil, but the tendency for rotation 
is not constant in value for all positions of the coil. When the 
coil is in a horizontal position, as shown by the cross-section in 
Fig. 162, the effect of the forces in tending to produce rotation 




























































ELECTRIC MOTORS 


229 


is at a maximum, because the two sides are then moving, as the 
coil rotates, perpendicular to the direction of the magnetic field. 
But for any other position of the coil with respect to the direc¬ 
tion of the magnetic field, such as the one in Pig. 163, the effect 
of the forces tending to produce rotation will be less, and this 
effect will continue to decrease as the coil moves from a position 
parallel to the field toward a position perpendicular to the field, 
as in Fig. 164, where the force producing rotation will be zero. 
The relation of the forces tending to rotate the coil for different 



Fig . 163_ When the coil is at an angle of 45 degrees, as here, the 

effect of the forces is less and will he for any position other than 

horizontal 


positions of one complete revolution may be represented by a 
curve, Fig. 165, in which points along the horizontal lines corre¬ 
spond’ to different positions of the coil as measured in degrees 
from a position perpendicular to the direction of the magnetic 
field. The relation of the lengths of the vertical lines correspond 
to the relation between the values of the forces tending to pro¬ 
duce rotation for the different positions. 

When the coil becomes perpendicular to the magnetic field 
the two commutator segments exchange positions with respect to 
the brushes, and as a result the current in the coil reverses 














































230 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

in direction. With a reversal in the direction of current in the 
coil, there is a reversal in the direction of the forces acting on 
the two sides, so that they tend to move across the magnetic 
field in directions opposite to those before the current in the coil 
was reversed. 

It is obvious from the preceding paragraphs that the force 
acting on the coil tends to produce a continuous rotation, pro¬ 
vided the magnetic field does not change in direction and that the 
brushes are properly placed on the commutator. The value of this 



Fig. 164 —When the plane of the coil is perpendicular to that of 
the magnetic field, as here, the force producing rotation is zero 


force, however, fluctuates in value. When the coil is perpen¬ 
dicular to the direction of the magnetic field it is zero, and 
if the coil should happen to stop in this position, there would be 
no tendency for rotation no matter how much current in the coil 
or how strong the magnetic field. Such an arrangement would 
not be at all satisfactory, on account of the fluctuation in the 
turning force on the coil and also because this force is zero for 
two positions of the coil in each revolution. The turning force 
may be made nearer constant in value and at no time zero by 
more coils and more commutator segments. 

















































ELECTRIC MOTORS 


231 


Multiple-Coil Armatures 

If two coils of wire, similar to the one described in the pre¬ 
vious section, be mounted on an axis at right angles to each 
other, with the four terminals connected to a four-part commuta¬ 
tor, the terminals of each coil being connected to opposite seg¬ 
ments, Fig. 166, then the force tending to turn the two coils will 
pulsate in value as follows: Since the two coils are at right 
angles to each other, the forces acting on them will likewise be 
at right angles to each other. If the currents in the two coils 
are equal in value when they are connected, assuming they remain 
so for one complete revolution, then the forces acting on the 
two coils may be represented by two curves, as in Fig. 167. 
Both coils do not carry current at the same time, since they are 



Fig. 165 —This curve shows the variation in the force tending to 
rotate a coil connected to a two-part commutator when it is 
placed in a uniform magnetic field. The angles are measured 
from a position when the plane of the coil is parallel to the 
magnetic field 

connected to independent commutator segments and the brushes 
rest on segments exactly opposite each other. Each coil is con¬ 
nected in circuit for each revolution only one-half of the time, 
but this time is split into two parts and each independent con¬ 
nection lasts only for one-fourth of a revolution. By properly 
placing the brushes it is possible to get a continuous turning 
force acting on the combination of coils, and the best position 
for the brushes is such that one coil is disconnected and the 
other one connected to the external circuit when they are mak¬ 
ing the same angle with the direction of the magnetic field, 
namely, 45 degrees. This position of the brushes corresponds 
to the point where the curves cross each other, Fig. 167, and the 









232 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


resultant force acting on tlie two coils may be represented by the 
upper parts of the curves, or the shaded portion. 

By increasing the number of coils and commutator segments 
the force acting on the coils will become nearer constant in 
value. This type of armature is not satisfactory for direct- 
current motors, as only those coils whose commutator segments 
are under the brushes at any particular time are in use. An 
armature winding of this type is called an open-circuit wind¬ 
ing. 

A better form of winding for direct-current motors, called a 
closed-circuit winding, makes use of all the coils all the time, 



Fig. 166 —When the terminals of two coils are connected to oppo¬ 
site segments of a four-part commutator, hoth coils do not carry 
current at the same time 


except when the two commutator segments to which a coil is 
connected are in contact with a brush or brushes of the same 
polarity. One of the simplest forms of closed-circuit windings is 
shown in Fig. 168, which consists of a ring with four coils 
wound about it and interconnected by means of four commuta¬ 
tor segments as in the figure. For convenience in referring to 
these coils they are designated by the letters A, B, C and D. 
The two coils A and C are short-circuited by the two brushes 
when they are in the positions shown in the figure. An instant 
later, however, coil A is in series with coil D on the left-hand 
side, and coil C is in series with coil B on the right-hand side, 


























ELECTRIC MOTORS 


238 

and this connection remains until coils B and D are short-circuited 
by the brushes. An instant later coil D is in series with coil 
C on the right-hand side, and coil B is in series with coil A on 
the left-hand side. It is apparent that the coils opposite each 
other are short-circuited by the brushes at the same time when 
they are symmetrically arranged, as in this case, and as one coil 
leaves the right-hand circuit and enters the left-hand circuit at 
the lower brush, a coil leaves the left-hand circuit and enters 
the right-hand circuit at the upper brush. With this arrange¬ 
ment of coils and commutator segments, all the coils are in 
circuit with the external circuit all the time, except when they 
are short-circuited by the brushes. If the position of the brushes 



Fig. 167 —The forces acting on the two coils connected as in Fig. 
106 may be represented by these curves. The magnetic field is 
assumed to be uniform 


is such that the coils are moving parallel to the magnetic field 
Avhen they are short-circuited, the total force acting on the com¬ 
bination tending to produce rotation will not decrease. The direc¬ 
tion of the current in each coil when it has moved from the short- 
circuited position is opposite to what it was just before it reached 
this position. Hence, the movement of the coil with respect to 
the magnetic field is reversed, that is, if it tended to move up 
or down before being short-circuited, it tends to move down or 
up after the short-circuiting. 

The total force tending to produce rotation at any instant is 
equal to the sum of the forces produced by each of the coils. 
When the coils are symmetrically placed with respect to each 
other, the force exerted by any two which are exactly opposite 
each other might be thought of as being due to a single coil 
having a number of turns equal to the sum of the turns in the 



234 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

two coils. The four coils in Fig. 168 are symmetrically arranged 
and may be treated as two coils instead of four. The force 
exerted on these two coils may be represented by two curves, 
A and D, in Fig. 169, and the total force at any time will be 
equal to the sum of the forces on the two coils, since they are 
both in circuit all the time, except when they are short-circuited 
by the brushes. Then the force exerted by that particular coil 
is zero, because it is then moving parallel to the magnetic field. 
This total force may be represented by a third curve, whose 
height at any point is equal to the sum of the heights of the 
curves A and D. From this figure it is readily seen that the 



Fig. 168 —The four coils in this form of closed-circuit winding are 
arranged symmetrically and, hence, may he treated as two coils 


force tending to produce rotation is not constant in value, but 
fluctuates between a minimum value equal to the maximum force 
produced by a single coil and a maximum value equal to the com¬ 
bined values of the forces produced by the coils when they are 
each midway between their positions of minimum and maximum 
force. The number of pulsations in the force per revolution 
may be increased by increasing the number of coils and commu¬ 
tator segments, and an increase in the number of pulsations pet 
revolution will result in a decrease in the difference between the 
maximum and the minimum values of the resultant force tending 
to produce rotation. Thus, with an increase in the number of 
coils and commutator segments, the resultant force becomes nearer 
constant in value, and the machine is capable of developing a 
fairly constant turning effort. 

The type of armature used in this arrangement—called a ring 













ELECTRIC MOTORS 


235 


type—is not used very extensively at present, but, on account 
of the simplicity in its construction and the connections of the 
coils, its operation is much more readily understood than that 
of the drum type, though the fundamental principle of both is 
exactly the same. After you have thoroughly mastered the 
operation of the ring type, the operation of the drum type, 
whether it be lap or wave wound, may be easily followed. 



Fig. 169 —This curve shows the variation in the force tending to 
turn a four-coil ring armature that has a four-segment commu¬ 
tator and is placed in a uniform magnetic field 


Types of Magnetic Fields 

In the majority of cases the magnetic field of a motor is pro¬ 
duced by electromagnets, though a magnetic field may be produced 
by powerful permanent horseshoe magnets. Small machines are 
usually bipolar, that is, they have one north pole and one south 
pole which create the magnetic field in which the armature rotates. 
These magnetic fields assume a number of different forms, three 
of which are shown in Figs. 170a, 170b and 170c. 

In larger machines it is customary to use multipolar field mag¬ 
nets, in which any even number of magnetic poles are arranged alter¬ 
nately around the armature, as in Fig. 171, which depicts a six- 
pole machine. 

The magnetic circuit of a motor whose magnetic field is created 
by electromagnets usually consists of five parts, Fig. 171, as follows: 
First, the field cores C are the parts about which the coils carrying 
the magnetizing current are wound. Second, the yoke Y con¬ 
nects the field cores together at the outer ends, as in the figure, and 
serves the double purpose of completing the magnetic circuit 
between the field cores and of providing the necessary mechanical 



236 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

supports for the cores. Some machines have no yoke in the mag¬ 
netic circuit, Fig. 170a. Third, the pole pieces P are the parts 
of the magnetic circuit next to the armature. They usually are 
cut to conform to the armature. They may be formed by properly 
shaping the ends of the field cores, or they may be pieces of metal 
entirely different from the ends of the field cores, being fastened to 
the field cores by bolts. The surfaces of the pole pieces next to the 
armature are called the pole faces and the projecting edges, when 
so constructed, are called the pole tips. Fourth, the armature 




Fig. 170a —Bipolar magnetic 
field unth single field coil. The 
magnetic circuit has no yoke 
as most types have 


Fig. 170b —Bipolar magnetic 
field with two field coils. Here 
a yoke supports the field cores 
and completes the circuit 


core A conducts the magnetic flux between air gaps and at the 
same time serves as a mechanical support for the armature winding. 
Fifth, the air gap G is the intervening space between the pole 
piece and the armature. 

When the field windings are placed on the magnetic circuit 
as in Figs. 170b and 171, the magnetomotive force created by the 
current in one coil is in series with the magnetomotive force 
created by the current in some other coil, or the magnetomotive 
force on any magnetic circuit is that produced by the two coils in 
series. If the field windings be placed on the magnetic circuit 
as in Figs. 170a and 170c, the magnetomotive force acting on any 
magnetic circuit will be equal to that produced by a single coil. 
When the field windings are as in Figs. 170b and 171 only half as 







































ELECTRIC MOTORS 237 

many ampere turns per coil as would be required if the coils 
were placed as in Figs. 170a and 170c will be required, assuming 
the total reluctance in the two cases to be the same. The magneto¬ 
motive force produced by the field coils in Fig. 171 acts upon two 
magnetic circuits and as a result is twice as effective as It would 
be if the coils were placed about the yoke between the poles. 

Materials Used in the Construction of the Magnetic Circuit of a 
Motor: Four materials commonly are used in the construction of 
the magnetic circuit of a motor, that is, wrought iron, cast iron, 
cast steel and sheet steel. Several factors govern the selection 
of the materials to be 
used in a particular ma¬ 
chine, such as initial 
cost, weight, efficiency 
demanded by purchaser, 
etc. 

The cheapest of these 
materials is cast iron, 
but its magnetic prop¬ 
erties are poorer than 
those of any of the oth¬ 
ers, so the saving in the 
initial cost of the iron 
per pound might be 
more than overbalanced 
by the fact that a larger 
bulk of cast iron would 
be required to form a 
certain magnetic circuit 
than would be required if wrought iron, for example, were used. 
There also would be an increase in the cost of copper required to 
magnetize the magnetic circuit of large area, since the length of 
each turn would be more than if a better material were used 
or the area of the magnetic circuit were reduced. 

Steel, on the other hand, is the best magnetic material and at 
the same time the most expensive. It is used where economy in 
weight and reduction in cross-section are desired. Machines used 
on electric motor cars, etc., are frequently made of cast or laminated 
steel on account of the large reduction in weight, which is a more 
important factor than the initial cost. 



polar magnetic field with single 
field coil 

























238 ELECTRICAL EQUIPMENT OP THE MOTOR CAR 

The magnetic circuits of motors are, as a rule, constructed of 
more than one material. Thus, the field cores may be of wrought 
iron, as that means a saving in copper since the length of the 
wire per turn would be less than if cast iron were used; the yoke 
may be of cast iron, as its area can be made larger than the 
field cores, and this increase in area will provide an ample magnetic 
circuit and also the mechanical strength necessary to support the 
field cores. The armature core usually is constructed of sheet metal 
to reduce the eddy-current loss to a minimum; the pole pieces may be 
a part of the field core and may be cast or laminated and bolted 
to the ends of the field cores. Numerous other combinations are 
used in the construction of the magnetic circuit of a motor, but 
these suggestions serve to illustrate some of the more important 
considerations involved in a proper selection of the materials for 
a particular case. 

Magnetic Leakage 

All the magnetic lines established by the field current of a motor 
do not pass through the armature core and, therefore, are not 
all useful in the operation of the motor. The ratio of the total 
number of magnetic lines that are produced to the number that are 
actually useful in the operation of the motor is called the co¬ 
efficient of dispersion. The value of this coefficient is always greater 
than one, as there are always more lines of force produced than are 
actually useful. It is desirable to have the value of the dispersion 
coefficient as low as possible, and this is accomplished by constructing 
the magnetic circuit so it will have no abrupt bends, be as short as 
possible and have a low reluctance. The coefficient of dispersion 
can be reduced by placing the field winding on or near that part 
of the magnetic circuit having the greatest reluctance and by so 
shaping the magnetic circuit that the paths conducting the magnetic 
flux which is not useful will have a high reluctance as compared 
to the paths conducting the useful magnetic flux. 

Excitation of Direct-Current Motors 

Direct-current motors may be divided into three classes according 
to the method employed in exciting the field magnets. These are: 
(a) Shunt motors; (b) series motors; and (c) compound motors. 

(a) The field winding of a shunt motor consists of a relatively 
large number of turns of small wire connected directly across the 
terminals of the machine or the circuit to which the machine is 


ELECTRIC MOTORS 


2 39 


connected. A rheostat may be connected in series with the field 
winding, which may be used in adjusting the value of the current, 
or no rheostat may be used at all, the field current being allowed 
to vary with the voltage impressed across its terminals and the 
change in the resistance of the field winding, due to a change in its 
temperature. The connections of a shunt motor are shown dia- 
grammatically in Fig. 172. The current in the field winding is 
independent of the current in the armature circuit as long as a 



Fig. 171 —This six-pole magnetic field is 
marked to show the different parts of the 
magnetic circuit 


change in armature current produces no change in the voltage 
impressed on the shunt field winding. 

(b) In the series motor, the field winding consists of a relatively 
few turns of large wire connected directly in series with the 
armature, as shown diagrammatically in Fig. 173. The current in 
the field winding is the same as the current in the armature, and the 
strength of the magnetic field of the machine varies with the 
armature current. The field strength does not increase as rapidly 


















240 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

as the current in the field winding, due to the fact that the reluc¬ 
tance of the magnetic circuit of the machine increases with an 
increase in the magnetic flux. In some cases a resistance is con¬ 
nected in parallel with the series field winding and only a part of 
the armature current passes through the field, the total current 
dividing inversely as the resistance of the two branches of the 
divided circuit. 

(c) The field windings of a compound motor are a combination 
of the shunt and series windings, as shown diagrammatically in Figs. 
174 and 175. The magnetic effcct'3 of these two windings may aid 
or oppose each other, depending on the manner in which they are 



armature 

connected. When the magnetizing actions of the series and shunt 
field windings act in the same direction about the magnetic circuit, 
the machine is called a cumulative compound motor; when the 
magnetizing actions of the series and shunt field windings are in 
opposite directions about the magnetic circuit, the machine is called 
a differential compound motor. In the case of the cumulative com¬ 
pound motor, the strength of the magnetic field increases with an 
increase in series field current, since the two magnetizing effects 
act together; in the case of the differential compound motor, the 
strength of the magnetic field decreases with an increase in series 

























ELECTRIC MOTORS 241 

field current, since the two magnetizing effects act in opposite direc 
tions. 

Direction of Rotation of Machine When Changed from a Gen¬ 
erator to a Motor: The direction in which a direct-current generator 
will operate when it is changed to a motor easily may be determined 
by the following simple relations. First, if both the direction of the 
armature current and the direction of the magnetic flux through 
the magnetic circuit of the machine remain unchanged, or if both 
are changed when the machine is changed from a generator to a 
motor, the direction of rotation will be reversed. Second, if either 
the direction of the armature current or the direction of the magnetic 



Fig. 173 —A series field winding; the field winding is in series with 
the armature and outside circuit 


flux through the magnetic circuit be reversed, but not both, when 
the machine is changed from a generator to a motor, the direction 
of rotation will remain unchanged. Third, to reverse the direction 
of rotation of a motor it is necessary to reverse either the direction 
of the armature current or the magnetic flux, but not both. 

If a shunt generator be changed to a motor, the polarity of the 
terminals remaining the same, the direction of rotation will remain 
unchanged, because the direction of the shunt field current remains 
the same and the armature current reverses in direction, it flowing 
from the negative to the positive terminal within the generator and 
from the positive to the negative terminal within the motor. If, 
however, the polarity of the machine be reversed when it is changed 























242 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

from a generator to a motor, the direction of rotation will remain 
unchanged, because the direction of the shunt current is reversed 
and the direction of the armature current remains constant. This 
leads to the general statement that a shunt generator when changed 
to a motor will operate in the same direction, regardless of the 
polarity of its terminals, provided there is no change in the con¬ 
nections of the armature and field windings with respect to each 
other. 

If a series generator be changed to a motor, the polarity of the 
terminals remaining the same, both the armature current and the 
magnetic flux will reverse in direction, and the direction of 



Fig. 174 —A cumulative compound field in which the magnetizing 
action of the shunt and series field windings act in the same 

direction 


rotation will reverse. If the polarity of the machine changes 
when it is changed from a generator to a motor, then the armature 
current and the direction of the magnetic field will remain unchanged, 
and the direction of rotation will be reversed. This leads to the 
general statement that a series generator when changed to a motor 
will operate in the opposite direction, regardless of the polarity of 
its terminals, provided there is no change in the connections of the 
armature and field windings with respect to each other. 

If a cumulative compound generator be changed to a motor with¬ 
out any change in the connections of the field windings, the machine 
will become a differential compound motor. Likewise, if the ma* 





































ELECTRIC MOTORS 


243 


chine is a differential compound generator, it will become a cumula¬ 
tive compound motor. The direction of rotation of such a machine 
when changed to a motor will depend on the relative effects of the 
series and the shunt field windings. For example, a differential 
compound motor may start up under the influence of the series wind¬ 
ing, and after the shunt field current has had time to build up in 
value the armature may stop and start to rotate in the opposite 
direction. 

Armature Reaction in a Motor 

When a current is in the armature winding of a motor a magnetiz¬ 
ing effect is produced, due to this current, and acts on the main 



Fig. 175 —A differential compound field in which the magnetizing 
actions of the shunt and series field windings are in opposite 

directions 


magnetic field of the motor. This effect is called armature reaction. 
The effect of this magnetizing action, due to the armature current, 
may be illustrated as follows: Take a simple two-pole drum arma¬ 
ture with a number of wires uniformly distributed over its surface 
and imagine it placed in a bipolar magnetic field, as in Fig. 176, 
which shows a cross-section through the armature and fields. Current 
is supplied to the armature winding by two brushes which rest on a 
commutator, and these brushes are placed in such a position that all 
the wires on the right of a vertical line through the center of the 
armature have a current in them from the surface of the paper and 
those on the left-hand side a current toward the surface of the paper. 




























244 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

If the magnetic poles have the polarity indicated in the figure, then 
the armature will tend to revolve in a counterclockwise direction, as 
indicated by the curved arrow. This direction of rotation easily 
may be determined by an application of the left-hand, or motor, rule. 
The plane, marked AC in the figure, which is perpendicular to the 
axis of the poles, and also the sheet of paper, is called the normal 
neutral plane. This normal neutral plane is perpendicular to the 
magnetic flux when there is no current in the armature winding. 
Now imagine the field current of the motor is zero and that a current 
is sent through the armature winding from some outside source. 
The current in the armature winding produces a magnetic field 



Fig. 176 —<Bipolar motor with magnetic field due to field current 

alone 


whose general direction through the armature core is downward, 
as in Fig. 177, when the current is in the direction indicated. 
Since the magnetizing effects of the armature current and the field 
current are present at the same time, they combine and form a 
resultant magnetizing effect which produces a magnetic field whose 
general direction is similar to that in Fig. 178. As a result of the 
magnetizing action of the armature current the magnetic field of a 
motor is twisted in a direction opposite to the direction of rotation of 
the armature, which is just the reverse of what occurs in the case of 
the generator. This twisting of the magnetic field results in the neu- 




































ELECTRIC MOTORS 


245 


tral plane, which is a plane perpendicular to the direction of the mag¬ 
netic field, being moved back of the normal neutral plane, as shown 
by the line AC in Fig. 178. 

Proper Position of the Brushes on a Direct-Current 

Motor 

In order that the armature produce its maximum turning effort 
for a given armature current and magnetic field, it is necessary 
that the brushes be placed on the commutator in such a position 
that the current in the conductors on the surface of the armature 
reverses in direction when the wires are moving parallel to the 



Fig. 177 —Bipolar motor with magnetic field due to armature cur¬ 
rent alone 

magnetic field, or when they are in the neutral plane. It is necessary 
then that the brushes be moved backward, or opposite to the direction 
of rotation in the case of the motor, as the current in the armature 
winding increases, which increases the amount the neutral plane is 
twisted or moved from the position it occupies when there is no 
current in the armature winding. The brushes are usually moved 












246 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


a little farther back than the neutral plane, though there is a slight 
reduction in the turning effort to improve commutation, as ex¬ 
plained in the section on Commutation. The position occupied by 
the brushes is called the commutating plane. The position the 
brushes actually occupy with respect to the poles of the machine 
will be quite different from that indicated in the figures dealing 
with armature reaction, so that the end connections of the wires to 
the commutator segments will be of the same length and form, but 
the direction of the current in the different wires will be the same as 
indicated in the figures. The brushes will occupy a position approxi¬ 
mately midway between the positions indicated in the figures. 



Fig. 178 —Bipolar motor with magnetic field due to combined 
magnetizing effects of armature and field currents . Note position 

of brushes 


With a change in the position of the brushes, the direction of 
the current in some of the wires on the surface of the armature 
will change. Thus, if the brushes are moved in a direction opposite 
to that in which the armature tends to rotate, as in Fig. 178, the 
direction of the current in the wires contained in the angle through 
which the brushes are moved will change, and the magnetic effect 
of a current in the armature no longer will be in a direction at right 
angles to the magnetizing effect of the field current but in a direc¬ 
tion similar to that in Fig. 179. This magnetizing effect of the arma¬ 
ture can be thought of as made up of two parts, one part acting per- 












ELECTRIC MOTORS 247 

pendicular to the magnetizing effect of the field current, called 
the cross-magnetizing effect, and the other part acting parallel 
to the magnetizing effect of the field current, called the demagnetiz¬ 
ing effect. The demagnetizing effect of the armature current tends 
to weaken the magnetic field of the motor, and the cross-magnetiz¬ 
ing effect tends to distort, or twist, the magnetic field in a direc¬ 
tion opposite to the direction in which the armature rotates. 

The angle between the commutating plane and the normal neutral 
plane is called the angle of lag in the case of the motor, because 
the brushes are moved backward or given a lag with respect to the 



Fig. 179 —Bipolar motor with magnetic field due to armature cur¬ 
rent alone and unth brushes moved back of normal neutral plane 


normal neutral plane, and it is called the angle of lead in the case 
of a generator, because the brushes are moved forward or given an 
angle of lead with respect to the normal neutral plane. 

Demagnetizing and Cross-Magnetizing Ampere-Turns 

The relative positions of the commutating planes for a generator 
and a motor are shown in Fig. 180, the full line representing the 
commutating plane of the motor and the dotted line representing 
the commutating plane of the generator. The direction of current 
in the armature wires corresponds to the motor connections, and 
the direction of rotation will be as indicated by the curved arrow. 
The wires between the two commutating planes on one side of the 









248 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

armature can be thought of as being in series with the wires be¬ 
tween the tw T o commutating planes on the opposite side of the 
armature and forming a number of complete turns about the 
armature core. The remaining wires may be thought of as forming 
a second set of turns. The product of the turns in the angle be¬ 
tween the commutating planes and the current in each of these 
turns gives the value of what is called the demagnetizing ampere- 
turns, because their effect is to produce a weakening of the magnetic 
field of the machine. The product of the remaining turns and the 
current they carry gives the value of what is called the cross-mag¬ 
netizing ampere-turns, because they act at right angles to the 



Fig. 180 —The two lines show the relative positions of the commu¬ 
tating planes of a motor and a generator 


magnetizing effect of the field current of the machine. The 
turns in the angle between the commutating planes are called the 
demagnetizing, or back, turns and the remaining turns are called 
the cross turns. 

Commutation 

The process of commutation can be explained by reference to 
a simplified diagram of the armature winding as shown in Fig. 181. 
The commutator segments are marked Cl, C2, C3, etc., while the 
various parts of the armature winding called elements and marked 
1, 2, 3, etc., are shown connected in series, the terminals of these 
elements being connected to the commutator segments in regular 










ELECTRIC MOTORS 


249 



order. The position of the neutral plane is represented by the line 
AC, the direction of rotation by the large curved arrow, the direction 
of the polarity of the part of the pole shown to the right by the letter 
S; and the current in the various elements of the winding by the 
small arrows. With the direction of current in the elements of the 
armature winding corresponding to that shown in the figure, the 
brush B must be negative in the case of a motor. 

As the armature rotates the commutator segments in turn pass 
under the brush, and if the arc of contact of the brush on the com¬ 
mutator is greater than the width of the insulation between the 
commutator segments, which always should be the case, then an 


Fig. 181 —Reference to this figure explains the process of commu¬ 
tation. The line AG represents the neutral plane 

element of the armature winding will be short-circuited when the 
brush is in contact with the two segments to which the terminals 
of the element are connected. When an element becomes short- 
circuited by the brush it is no longer directly in series with the 
elements of the armature winding to its right or left, and the current 
in the element will drop to zero value, provided there is no electro¬ 
motive force induced in the element, or it is moving parallel to the 
magnetic field. It does not do so instantly on account of a property 
of the element, called its inductance, which tends to prolong the 










250 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

current. As the armature rotates one of the commutator segments 
to which the short-circuited element is connected moves out from 
under the edge of the brush and the short-circuit on the element 
is removed, and the element becomes a part of the circuit through 
the armature to the left of the brush. When the element which 
was short-circuited becomes a part of the left-hand path through 
the armature, it must carry the same current the other elements 
in that path carry, regardless of the value of the electromotive 
force being generated in the element, because they are all directly 
in series. If the short-circuited element has zero current when 
the short-circuit is removed' by one of the segments moving from 
under the brush, the current in the element must increase almost 
instantly to a value equal to the current in the elements in the 
left-handed circuit through the armature. A property of the ele¬ 
ment, inductance, opposes this sudden increase in current, and as 
a result there is a tendency for an arc to form between the edge 
of the brush and the commutator segment which is breaking con¬ 
tact with the brush until the current in the element whose short- 
circuit is being removed has reached its proper value, or the in¬ 
ductance of the coil has been overcome. This condition of affairs 
would result in a continuous sparking at the brushes, which would 
not only represent a loss but would be injurious to both the com¬ 
mutator and the brushes. 

Sparking due to the cause just mentioned can be reduced and 
practically overcome by moving the brushes back of the neutral 
plane. When the brushes are thus changed, an electromotive force 
will be induced in the element of the winding while it is short- 
circuited, and this electromotive force will be in a direction such 
as to produce a current in the element in the same direction as the 
current in the elements to the left of the brush. The induced electro¬ 
motive force in the element which is short-circuited also causes the 
current in the element, when it comes into the short-circuited posi¬ 
tion, to decrease to zero value in a less time than it would if there 
were no induced electromotive force in the element. The above 
results, due to the effect of the induced electromotive force in the 
short-circuited element, indicates that the inductance of the ele¬ 
ment is overcome while it is short-circuited, and a current of the 
proper value will be established already in the element when it 
becomes a part of the left-hand circuit. Moving the brushes 
back of the neutral plane results in a decrease in the turning 


ELECTRIC MOTORS 251 

effort the armature is capable of producing, but this is more than 
offset by the advantages of better commutation. 

The winding which has been used in explaining commutation is 
perhaps the simplest form possible, but the fundamental principles 
involved are practically the same in every case. 

In certain types of lap windings the elements are connected to 
segments which are not adjacent to each other but may be several 
segments apart. In such a winding, it is necessary that the arc 
of contact of the brushes cover several segments in order that the 
various elements may be commutated properly. The time of short- 
circuit of the different elements must be such that it is possible 
to reverse the current in the element. 

In the case of wave windings, the elements are connected to 
commutator segments which are approximately 360 electrical de¬ 
grees apart, and instead of an element being short-circuited by a 
single brush, as in the lap winding, it is short-circuited by two 
brushes of the same polarity, these brushes being connected ex¬ 
ternally by a heavy conductor, called the brush ring. 

The brushes on a machine may be adjusted to give practically 
perfect commutation for a given field current and armature current, 
but’ if either the field or the armature current, or both, change 
in value, there will be a change in the degree to which the resultant 
magnetic field of the machine is twisted, and, as a result, the com¬ 
mutation will not be as satisfactory as before the change. To 
have as good commutation as possible at all times, it would be 
necessary to move the brushes whenever the position of the neutral 
plane is changed. 

Commutation is improved somewhat by increasing the resistance 
of the short-circuited element, though there is a slight decrease 
in efficiency, due to the introduction of this resistance in the main 
armature circuit. When the resistance of the short-circuited ele¬ 
ment is increased, the current can be reversed in direction in a shorter 
time than with the lower resistance. Carbon brushes have the 
advantage of giving better commutation than copper brushes, as 
they offer a higher resistance in the path of the short-circuited 
element than the copper brushes do. They are sometimes copper- 
plated to reduce their resistance in the main circuit of the machine. 

Reducing Armature Reaction 

Armature reaction interferes with the satisfactory operation of 
the motor, and it always is desirable to reduce it to a minimum where 


252 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

possible. There are several methods of bringing about a reduction 
in armature reaction, some of the more important ones being: 

(a) By constructing the machine with a relatively long air gap; 

(b) By slotting the pole cores parallel to the axis of the armature 
core; 

(c) By properly shaping the pole pieces. 

(a) Increasing the length of the air gap increases the reluctance 
of the magnetic circuit, and more ampere-turns are required to pro¬ 
duce the necessary magnetic flux than would be required with a 
shorter air gap. The effect of the cross ampere-turns on the arma¬ 
ture in distorting the magnetic field is not so great when many 
ampere-turns per pole are required, as it is with fewer ampere-turns 

per pole. As a result, 
the position of the neu¬ 
tral plane of the ma¬ 
chine remains more 
nearly constant. 

(b) Cutting slots in 
the pole cores parallel 
to the axis of the arma¬ 
ture core introduces a 
larger reluctance in the 
path on which the cross 
magnetizing ampere- 
turns act but does not 
introduce anything like 
as great a reluctance in 
the main magnetic cir¬ 
cuit of the machine. 

(c) The shifting of 
the magnetic flux across the pole shoes of the machine can be reduced 
readily by shaping the pole faces so that the parts of the air gap 
where the magnetic flux tends to become most dense will have the 
greater reluctance. Thus the pole tips may be chamfered, as in 
Fig. 182, or the bore of the pole faces may be made eccentric with 
respect to the armature, as in Fig. 183. Additional reluctance at the 
pole tips may be provided by using a long thin tip or, in the case of 
laminated poles, by using a stamping of the form shown in Fig. 184, 
in which case the laminations are built up to the required thickness in 
such a manner that the projecting tips are on alternate sides. This 



Fig. 182 —Chamfered pole shoes reduce 
the shifting of the magnetic flux 







ELECTRIC MOTORS 2t>3 

construction may be used for the pole pieces alone and then bolted to 
a solid pole core. 

Counter-Electromotive Force 

When the armature of a motor revolves in the magnetic field of 
the machine, an electromotive force is induced in the wires on the 
surface of the armature, called conductors, just the same as there 
would be if the machine were operated as a generator. Since the 
relation between the direction of motion of a wire carrying a current 
when it is placed in a magnetic field and the direction of the magnetic 
field in the case of a motor is opposite to what it is in the case of a 
generator, the direction of the current in the wires and the direction 
of the magnetic field re¬ 
maining constant, the in- 
d u c e d electromotive 
force in the armature 
winding of the motor 
will be just the reverse 
of what it is in the case 
of the generator. 

This induced' electro¬ 
motive force acts in a 
direction just opposite 
to the impressed electro¬ 
motive force which is 
producing the current 
in the armature wind¬ 
ing, and, for that rea¬ 
son, it is called the coun¬ 
ter-electromotive force 
of the motor. The counter-electromotive force of a motor depends 
on the same thing on which the generated electrical pressure in a 
generator depends. It increases with an increase in speed and de¬ 
creases with a decrease in speed, all other conditions remaining the 
same. It also increases with an increase in the field strength of 
the motor and decreases with a decrease in field strength, all other 
conditions remaining the same. 

The counter-electromotive force of a motor under normal condi¬ 
tions cannot exceed in value the voltage of the circuit to which it is 
connected; just as the voltage of a battery which is being charged 



Fig. 183 —Eccentric pole shoes also in¬ 
crease the reluctance at the pole tips 







254 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

cannot rise above the voltage of the circuit to which it is connected. 
If the electromotive force in the armature of a motor for any reason 
should exceed the voltage of the circuit to which it is connected, the 
action in the machine will change from that of a motor to that of a 
generator and will deliver current to the circuit to which it is con¬ 
nected just as a battery will deliver current to a circuit to which it 
is connected if the voltage of the battery exceeds the voltage of the 
circuit and the battery discharges instead of charging. In the motor 
the electricity is flowing in the opposite direction to the pressure and 
is doing work, and this work is transformed in the motor from 
electrical work into mechanical work, a part of which is delivered 
by the motor to the device it may be operating. 

Torque Produced by a Motor 

The torque of a motor is its turning effort, which is measured in 
pound-feet, as explained in one of the early chapters. There are 

several things on which the 
torque of a motor depends, 
but only two of these may 
be changed after the motor 
is constructed, namely, the 
field strength and the arma¬ 
ture current. An increase 
or decrease in the value of 
either the field strength or 
armature current or both 
results in an increase or de¬ 
crease in the torque. It is obvious from the above statement that the 
torque of a motor will increase more rapidly when the field strength 
and armature current are both increasing than it will when either the 
field strength or armature current are increasing alone. 

Speed of a Motor 

The speed of a motor will always be such, when it has reached a 
constant value, that the torque produced is just ample to drive the 
load connected to the motor. Since the torque depends on the value 
of the field strength and the armature current, it is evident that the 
constant speed at which a motor will operate when driving a certain 
load will depend on the field strength and the armature current. The 
armature current taken by a motor will be equal to the voltage of 



Fig. 184 —The projecting tips of lam¬ 
inated poles are on alternate sides 









ELECTRIC MOTORS 


255 


the circuit to which the motor is connected minus the counter-electro¬ 
motive force generated in the armature of the motor divided by the 
resistance of the armature circuit. The counter-electromotive force 
depends on the field strength and the speed. 

In general then, the speed of a motor will always be such that the 
counter-electromotive force generated at that speed will permit the 
proper amount of current to pass through the armature in order that 
the torque developed is just ample to drive the load at that par¬ 
ticular speed. If the load on the motor should increase for any 
reason, the torque that is being developed is no longer ample to drive 
the load or maintain the speed; hence there is a decrease in speed, 
which results in a decrease in the counter-electromotive force and 
in turn an increase in armature current and an increase in torque. 
The speed will continue to decrease and the torque to build up until 
the torque has increased to a value just ample to drive the in¬ 
creased load. Likewise, should the load on a motor decrease the 
torque it is developing will be more than is required to drive the 
load, and as a result there will be an increase in speed. This 
increase in speed results in an increase in counter-electromotive 
force, which causes the current to decrease, and hence the torque 
decreases. The increase in speed will continue until the torque 
has been reduced to a value just ample to drive the load the 
motor is connected to. 

Output of a Motor 

The output of a motor depends on the torque the motor is develop¬ 
ing and the speed at which the motor is operating. If the torque be 
measured in pound-feet and the speed in revolutions per minute, then 
the output of the motor in horsepower may be determined by the 
following equation: 

6.2832 X torque X revolutions per minute 

Output in horsepower = --—- 

33,000 

It is evident from the above equation that the horsepower the motor 
is delivering will vary directly as the torque if the speed remains 
constant and directly as the speed if the torque remains constant. 

Operation of the Shunt Motor 

The connections of a shunt motor are shown diagrammatically in 
Fig. 185. In this particular case the motor is arranged to be 
operated from a three-cell storage battery. When the switch S is 



256 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

closed a current whose value will depend on the voltage of the battery 
and the resistance of the field circuit will be established in the field 
winding and at the same time a current will be established in the 
armature circuit. The current in the armature will react on the 
magnetic field produced by the field current, and a torque will be 
produced, which will cause the armature to rotate unless the load 
on the motor happens to require a greater driving torque than the 
motor is capable of producing. Assuming the torque the motor is 
producing is ample to start the load, then the speed will increase, 
which causes the counter-electromotive force to increase, it being 
zero in value while the armature is standing still, and as a result there 
will be a decrease in the current in the armature and hence a decrease 
in the torque developed. 

The speed will continue to increase and the torque to decrease 
until the torque developed is just ample to drive the load at the 



Fig. 185 —Shunt motor connected to a three-cell battery 


particular speed it is then operating. Any change in load on the 
motor will mean a change in the torque the motor is required to 
develop, and hence a change in speed will take place and the current 
in the armature will adjust itself to the required value to produce 
the desired torque. With an increase in load there will be a decrease 
in speed, but this decrease, in the ordinary shunt motor, ordinarily 
will not amount to a great deal in percent of the motor’s rated 
speed, as a very small decrease in speed will result in the necessary 
decrease in counter-electromotive force. As a rule the counter¬ 
electromotive force differs from the impressed voltage acting on the 
motor by a very small amount. 

The relation between torque and armature current and speed and 
armature current may be represented graphically, as shown in Fig. 
188. If the field strength of the motor were to remain constant the 


















ELECTRIC MOTORS 257 

torque would increase directly as the armature current. Since there 
is a weakening of the magnetic field, due to armature reaction and 
other causes, the torque will not increase quite as rapidly as the 
current, and this increase will grow less and less rapid as the current 
increases in value, which accounts for the curve in the figure, marked 
torque, not being a straight line. 

The speed of the shunt motor decreases with an increase in current 
in order that there be the proper reduction in counter-electromotive 
force so that the current may increase and thus produce a greater 
torque. 

Operation of the Series Motor 

The connections of a series motor are shown diagrammatically in 
Fig. 186. When the switch S is closed a current will be produced by 
the battery in the armature and field circuits in series. The value 



Fig. 186 —Series motor connected to a three-cell battery 


of this current, at the instant the circuit is closed, will be equal to 
the voltage of the battery divided by the total resistance of the cir¬ 
cuit, and it will have its maximum possible value, since no counter 
pressure is generated in the armature of the motor when it is stand¬ 
ing still. This large current will produce a very strong magnetic 
field, and hence a maximum torque will be developed. This torque 
will cause the armature to rotate, unless the torque required to drive 
the load exceeds that of the motor, and just as soon as the armature 
starts to rotate a counter-electromotive force will be generated, which 
will cause a decrease in armature current and hence a decrease in 
torque. When the torque has decreased to a value just ample to drive 
the load at the speed at which it is then operating, the speed of the 
motor will become constant. As the motor speeds up there is a de¬ 
crease in torque, due to a decrease in armature current and also due 
to a decrease in field strength. If the load on the motor is decreased, 


















258 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the torque the motor is developing is more than ample to drive the 
load, and it immediately starts to increase in speed. The increase in 
speed means an increase in counter-electromotive force and a decrease 
in armature and field current. The decreasing field current causes 
the field strength to grow less, which tends to lower the counter¬ 
electromotive force. This tendency of the decreasing field 
strength to lower the counter-electromotive force in effect 
does not amount to as much as the increase in speed, which 
results in the counter-electromotive force increasing. The in¬ 
crease, however, is not as much as would take place, due to a given 
change in speed, if the field strength remained unchanged. Hence, 
in order to bring about the required increase in counter-electromotive 
force with a decrease in load on the series motor there will be a 
greater increase in speed than in the case of the shunt motor. 

The relation between speed and armature current for a series 
motor is shown in Fig. 187. When the load is removed entirely 
from a series motor the only torque it is required to develop is that 
necessary to revolve the armature. This small torque means a small 
armature and field current is required. The small field current means 
a very weak field, and the speed will be high in order that the proper 
counter-electromotive force be generated by revolving the armature 
in the weak field. In some cases this speed may become dangerously 
high, and for this very reason it is not advisable to try to operate a 
series motor when it is disconnected from a load. 

The torque of a series motor increases more rapidly as the cur¬ 
rent in the armature increases than it does in the shunt motor. The 
reason for this is due to the fact that the field strength is increasing 
at the same time the armature current is increasing. The relation 
between torque and current is shown by the curve marked torque in 
Fig. 187. The characteristics of the series motor as pointed out 
above are such that it is much better adapted to the requirements 
of a motor to be used in starting the gasoline engine than the shunt 
motor. 

Compound Motor 

The compound motor is a combination of the series and shunt. 
When the magnetizing action of the series field opposes the mag¬ 
netizing action of the shunt field the machine is called a differential 
compound motor. When the magnetizing action of the two fields 
act in the same direction the machine is called a cumulative com¬ 
pound motor. 


ELECTRIC MOTORS 


259 


In the case of the differential compound motor, the field strength 
is weakened as the current the motor takes increases and as a result 
there is not as much of a decrease in speed in order that the counter¬ 
electromotive force decrease to the required value as there would be 
if the field strength remained constant. It is possible in such a 
motor to maintain the speed practically constant for all load cur¬ 
rents by properly adjusting the magnetizing effect of the series 
fields. The torque of a differential motor does not increase as rapidly 



ARMATURE CURRENT 


ARMATURE CURRENT 


Fig. 187 —Relation of torque 
and speed to armature current 
for a series motor is repre¬ 
sented here 


Fig. 188 —These curves cho'O 
relation of torque and speed to 
armature current for a shunt 
motor 


with an increase in armature current as it would if the field remained 
constant in strength. 

The characteristics of the cumulative compound motor are be¬ 
tween those of the shunt and series motor, it being a combination 
of the two so far as the magnetizing action of the field windings 
are concerned. 

Starting Motors 

When the armature of a motor is connected directly to the source 
of pressure a current whose value is equal to the pressure divided by 
the resistance of the circuit will be produced. In some cases this 
current is excessive, and in such cases it is necessary to connect a 
variable resistance in series with the armature. As soon as the arma¬ 
ture starts to rotate a counter-electromotive force will be generated, 










































260 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

which causes the current to decrease in value, and the resistance may 
be decreased in value and finally removed from the circuit. Such a 
device is called a starting box, but it is used little with motor car 
motors, as the motors usually are designed to carry the maximum 
current the battery will send through them for a short time when 
the armature is at a standstill. 

Motor-Generator 

The motor-generator is a combination of a motor and a genera¬ 
tor, mechanically connected together and usually mounted on 
a common metal or wooden base. The motor of-such a combination 
may be either a direct-current or an alternating-current motor, and 
it may be constructed to operate on any reasonable value of voltage, 
depending on the particular requirements. Likewise, the generator 
may be one capable of delivering either direct-current or alternating 
current, and this current may be delivered at almost any voltage, de¬ 
pending on the requirements, which determine the construction of 
the generator. When the two machines are coupled directly together 
by a flexible coupling their speed will be the same. If a belt or gear 
is used in connecting them, their speeds may be the same or different, 
depending on the size of the pulleys or gears used. The electrical 
operation of the motor is entirely independent of the generator. The 
field of either machine may be varied in strength without changing 
the field of the other machine. 

A combination of two machines forming a motor-generator set is 
shown in Fig. 189. A motor-generator outfit may be used in chang¬ 
ing alternating current at one voltage into direct current at some 
other voltage or vice versa, or it may be used in increasing or de¬ 
creasing alternating or direct-current voltage. For example, sup¬ 
pose only alternating current is available and you wish to charge 
storage batteries. The motor element of your motor-generator should 
be an alternating-current motor of such a construction and voltage 
that it will operate on the alternating-current circuit from which you 
are to obtain the electrical energy. The generator element should 
be of such a construction that it will deliver the required current and 
at the proper voltage. The horse-power capacity of the motor always 
should be such that it will drive the generator when the generator is 
delivering its full load. 

In some cases direct-current is available but at such a voltage that 
it cannot be used economically in charging storage batteries unless 


ELECTRIC MOTORS 


261 



the batteries be connected in series, which is quite inconvenient and 
often times impossible. In such cases it often results in a large sav¬ 
ing to install a motor-generator set composed of two direct-current 
machines, the motor being constructed to operate on the voltage avail¬ 
able and the generator to deliver current at the proper voltage to 
charge the batteries. Remember that the output of the generator in 
watts would be equal to the input t:> the motor in watts if there were 
no losses in the machines. That is, if the voltage of the generator 


Fig. 189— This motor generator consists of an alternating-current 
motor, left, which drives a direct-current generator, right 

is less than the voltage of the motor, then the current the generator 
will deliver will be greater than the current taken to operate the 
motor. On account of losses in the two machines the output of the 
generator is always less than the input to the motor. 

Dynamotor 

The dynamotor is a machine having an armature with two windings 
and provided with two commutators which may be mounted on the 
same or opposite ends of the armature. Both of these windings re¬ 
volve in the same magnetic field, and any change in the strength of 
the magnetic field will influence the value of the voltage generated 
in both windings. The voltage generated in the two windings will be 
the same if there are the same number of turns about the armature 
in each of the windings. If the number of turns in the two windings 
are unequal the voltages generated in the two windings will bear the 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


2f>2 

same relation to each other as exists between the number of turns, 
the winding of larger number of turns having the greater voltage 
induced in it. 

Both of these windings may be used to deliver current; that is, 
both windings will act as generators when the armature of the ma¬ 
chine is driven in some way as by a motor or gas engine. 

One winding may be used as a motor and drive the other winding 
in the magnetic field, and it will act as a generator and may deliver 
current. The voltage at which the generator "winding will deliver 
current depends on the ratio between the number of turns in the 
two windings and the voltage applied to the motor winding, neglect¬ 
ing voltage losses in the two windings. This voltage relation is fixed 
by the relation of the turns in the two windings and cannot be 
changed by varying the strength of the magnetic field as in the case 
of the motor generator for the following reasons: 

If the field of the dynamotor be increased in strength in an at¬ 
tempt to increase the voltage generated in the generator winding, 
there will be a decrease in speed of the armature, as the necessary 
counter-electromotive force now will be generated in the motor wind¬ 
ing at a lower speed since the field strength has been increased. 
This decrease in speed of the armature counteracts the effect of the 
increase in field strength so far as the generator winding is con¬ 
cerned, which results in the voltage generated in the generator wind¬ 
ing remaining practically constant. If the voltage applied to the 
motor winding be increased or decreased there will be a proportion¬ 
ate increase or decrease in the voltage produced in the generator wind¬ 
ing. The fixed voltage relation in the dynamotor is its chief disad¬ 
vantage when used in charging storage batteries, as the current sent 
through the battery must be adjusted by a series resistance rather 
than by varying the field of the generator as in the case of the 
motor generator. 

The Dynamotor as a Starting and Lighting Unit 

The dynamotor is used by several different companies in place of a 
separate generator and motor. The electrical and mechanical con¬ 
nections of the machine are such that the generator and motor actions 
are taking place at different times. A good practical example of the 
use of the dynamotor is found in the Delco system shown in Fig. 190. 
The terminals of the two sets of windings are brought out at oppo¬ 
site ends of the armature and connected to separate commutators. A 


ELECTRIC MOTORS 2G3 

diagram of the two windings is given in Fig. 191. There are nine¬ 
teen segments in the commutator of the motor and just twice as 
many, or thirty-eight, in the commutator of the generator. These 
windings are placed in the same slots in the armature core. The 
magnetic field of the machine is produced by either a shunt or series 
coil, depending on whether the machine is acting normally as a gen¬ 
erator or as a motor. The operation of the Delco dynamotor may be 
divided into three distinct parts, and these are: 

(a) Motoring the generator. 

(b) Cranking the engine. 

(c) Generating electrical energy. 

Before discussing each of the above operations it will be best to 
explain what changes in connections take place when the ignition 



Fig. 190 —!Side view of Delco dynamotor, which usually is called a 
motor generator 


switch is closed and the starting pedal is pressed down. Closing the 
ignition switch connects the generator armature winding and shunt 
field across the terminals of the storage battery. As the starting 
switch is pressed down one of the brushes on the commutator of the 
motor, which normally is raised from the surface of the commutator, 
is lowered; a switch in series with the armature of the generator is 
opened; and the gears used in cranking the engine are thrown in 
mesh. See Fig. 192. 

(a) When the armature and field of the generator are connected to 
the battery by closing the ignition switch a motor action takes place 










































264 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

in the generator armature winding, and the armature starts to re¬ 
volve. The connection between the shaft of the dynamotor and the 
engine is made by a form of over-running clutch which only transmits 
power when the shaft driven by the engine tends to run at a greater 
speed than the shaft of the dynamotor. This clutch, called the gen¬ 
erator over-running clutch, allows the armature of the dynamotor to 
revolve freely, when the engine is standing still, in the same direc¬ 
tion as it is rotated by the engine when the dynamotor is being 
operated as a generator. 

(b) The motoring of the generator assists in bringing the gears 
into mesh when the starting pedal is pressed down. Lowering the 
brush on the commutator of the motor closes the motor circuit, which 
is composed of the motor armature winding and series field connected 




Fig. 191 —Comparison of motor and generator windings on Delco 

dynamotor 


in series to the battery. At the same time, the motor action in the 
armature of the generator is stopped as the generator switch is 
opened. The dynamotor now is operating as a series motor and driv¬ 
ing the engine. As soon as the engine starts to fire the motor will 
cease to transmit power to the engine, as a second over-running clutch 
in one of the gears allows the speed of the shaft driven by the engine 
to exceed the speed of the shaft of the dynamotor. The starting 
pedal now should be released, which raises the motor brush and closes 
the generator circuit. 












































































































ELECTRIC MOTORS 


265 


(c) As soon as the engine speeds up power will be transmitted to 
the dynamotor through the generator over-running clutch. If the 
generator switch is closed a generator action will take place in the 
generator armature winding, provided the voltage in this winding 
exceeds the voltage of the battery to which the brushes of the gen¬ 
erator are connected. When the voltage in the generator armature 
winding drops below the voltage of the battery, due to any cause, the 



generator will be changed to a motor, and power may be transmitted 
to the engine through the motor over-running clutch. A more com¬ 
plete description of this and other similar systems will be given later 
when the various complete systems are discussed in detail. 




























CHAPTER XVII 


Motor and Engine Connection 

General Requirements of Starting Motor 

HE chief function of the starting motor is to turn the gasoline 



I engine over at such a speed that it readily may be started, 
which, in the majority of cases is between 100 and 200 r.p.m., as¬ 
suming the position and intensity of the spark, as well as the gas 
mixture and other conditions are approximately correct. If the 
starting motor is connected to the engine in such a manner that 
it must operate at the same speed as the engine, it is evident that 
it must be capable of developing sufficient torque so that the torque 
available at the gear or pulley on its shaft is just equal to that re¬ 
quired to drive the engine at the desired speed. 

On the other hand, if the connection between the motor and 
engine be made in such a manner that the motor may run much 
faster in r.p.m. than the engine, the torque the motor must be 
capable of producing at the gear or pulley on its shaft will bear, 
neglecting losses, the same relation to the torque required to 
drive the engine as the speed of the engine bears to the speed 
of the motor. 

For example, if a certain engine requires a torque of 20 pound 
feet to drive it at a speed of 150 r.p.m. and the starting motor 
is geared to the engine in such a manner that it operates at forty 
times the speed of the engine, then the torque the motor must be 
capable of delivering at its gear or -pulley will be, neglecting 
losses, equal to one 1/40 of 20 or .5 pound feet. The losses between 
the gear on the motor shaft and the shaft of the engine must 
be taken care of by the motor in addition to driving the engine; 
that is, the actual torque of the motor will always be greater 
than the theoretical torque required, due to these losses. The 
losses in some gear types of transmissions may amount to as much 


MOTOR AND ENGINE CONNECTION 207 

as 40 per eent, while the manufacturers of certain types of chain 
transmissions claim the losses are as low as 5 per cent. 

The size of an electric motor capable of delivering a certain 
horsepower depends on the speed at which the motor is to be 
operated, there being an increase in size with a decrease in speed 
and, conversely, a decrease in size with an increase in speed. On 
account of the limitations in size of the starting motor, due to 
space and weight requirements, it is obvious that it would be 
better to have the speed at which the motor operates greater 
than the speed of the engine. There are several exceptions to 
this last statement, and the principal ones are found in the 
U.S.L. outfit, the Woods dual power car and the Owen Magnetic, 
all of which will be explained in detail later. 

The main requirement of the connection between the electric 
motor and the engine is to provide a positive mechanical connec-. „ 
tion so that the power developed by the motor may be trans¬ 
mitted to the crankshaft of the engine. This mechanical connec¬ 
tion is required only when the motor is driving the engine, and 
the construction and operation of the intermediate device should 
be such that power may be transmitted in one direction only. 
This can be explained better by assuming a definite case. 

Suppose the ratio between motor and engine speeds in a certain 
installation is 30 to 1 and that the motor will operate the engine 
at 125 r.p.m. When the engine starts to fire, it is operating at 
approximately 125 r.p.m. and the motor is operating at 3,750 
r.p.m. The speed of the engine will increase, and when it reaches 
a speed of 500 r.p.m. the speed of the motor will be 15,000, which 
is considerably above the safety limit, and the motor should be 
disconnected from the engine long before this speed has been 
reached. 

Several different devices are employed to overcome the above 
difficulty, such as the ordinary jaw clutch similar to that employed 
on all hand cranks, friction clutch, roller overrunning clutch, 
w ratchet-and-pawl overrunning clutch, worm-and-worm-wheel, Ben- 
dix drive, electromagnetic-operated pinions, mechanically-operated 
pinions, etc. 

Overrunning Jaw Clutch 

A type of clutch similar to that used in connecting the starting 
crank to the crankshaft of a motor first was used in connecting 
the starting motor to the engine. This clutch consists of a number 


2(58 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of jaws on two opposite surfaces with their backs beveled and 
arranged so that they will mesh with each other; but power can 
be transmitted in one direction only, as the jaws will slide past 
each other when the portion of the clutch being driven tends to 
exceed the speed of the driving portion. This type is little used, 
due principally to the fact that it gives a clicking noise when 
the engine runs away from the starting motor, as it will do imme¬ 
diately after each piston has passed its position of maximum 
compression. 

An example of the application of a clutch of this type is shown 
in Figs. 193, 194 and 195. When the upper end of the clutch 



Fig. 193 —Type of clutch first 
used in connecting starting 
motor to engine 


Fig. 194 —A further detail of 
the same clutch. It is little 
used 


actuator is moved toward the right the left-hand portion of the 
clutch shown in Fig. 193 will move along the end of the crank¬ 
shaft, and the teeth become engaged with the teeth on the surface 
of the large sprocket. This sprocket turns freely on the end of 
the crankshaft when the clutch is disengaged, being driven by a 
chain which runs over a second and smaller sprocket mounted on 
a shaft as shown in Fig. 194, which in turn is driven by the 
starting motor through a worm-and-worm gear as shown in Fig. 
195. As long as the large sprocket in Fig. 193 tends to turn faster 
































MOTOR AND ENGINE CONNECTION 269 

in a clockwise direction as viewed from the left-hand end, or 
front, of the engine than the left-hand part of the clutch, the 
two portions of the clutch will remain engaged, but just as soon 
as the speed of the engine exceeds that of the large sprocket 



Fig. 195 —The motor turns the sprocket through the worm- 
and-icorm gear. When the engine runs away from the motor 
the clutch gives a clicking noise 


the clutch becomes disengaged and the two surfaces move relative 
to each other, giving a clicking sound. 

Overrunning Roller Clutch 

There are several different forms of roller clutches, but in prin¬ 
ciple they are the same. For this reason a typical form, such as 


















270 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the one used by Gray & Davis, will be described. The construc¬ 
tion of the clutch is shown in Fig. 196, and it consists of two prin¬ 
cipal parts, the outer ring B and the clutch center C. The outer 
portion of the clutch may be driven by gears, chain drive, or it 
may be connected rigidly to the driving shaft. In this particular 
case power is transmitted to R by the pinion P, and it is arranged 
to drive the inner portion C in a clockwise direction. Several 



Fig. 196 —This illustrates the principle of the 
overrunning roller type clutch 


slots are cut in the outer surface of the portion C, four in this 
particular case, and the depth of these slots varies from one side 
to the other, being deeper on the right-hand side of each slot 
when the slot is in its uppermost position. 

Rollers are placed in these slots as shown at B with their axis 
parallel to the axis of rotation of the clutch—that is, the rollers 
are parallel to the shaft E—and they are held away from the 
deeper side of the slot by a suitable plunger, Cj and spring, D. The 
diameter of these rollers is a little greater than the depth of the 
slots on their shallow side, and as a result the springs cannot 







MOTOR AND ENGINE CONNECTION 


271 


force the rollers completely over against the side of the slots. 
When the outer ring R of the clutch is rotated in the direction of 
the arrow A the rollers will be wedged between the inner sur¬ 
face of the ring R and the bottom of the slots. With the rollers 
thus wedged tightly between the two parts of the clutch, the 
inner part C will be rotated in the same direction and at the 
same speed as the outer portion R, and power may be transmitted 
from R to C, which in turn may be connected through gears, chain 
or direct, to the crankshaft of the engine. In this particular 

case the inner portion of 
the clutch is keyed to the 
shaft E. 

Just as soon as the 
starting motor starts to 
revolve the pinion P the 
outer portion of the clutch 
will start to revolve, and 
the locking action just de¬ 
scribed will take place be¬ 
tween the two parts R and 
C almost instantly, which 
results in the cranking ac¬ 
tion taking place at once. 
The cranking action of 
the motor will continue 
until the engine starts to 
fire, when its speed will in¬ 
crease. This results in 
the speed of the inner por¬ 
tion of the clutch exceed¬ 
ing the speed of the outer portion, and the two parts no longer will 
be locked together, as the rollers then will tend to roll into the 
deeper part of the slots, due to the fact that the piece C is traveling 
faster than the inner surface of the piece R, and the direction in 
which the rollers turn about their own axis will be just the reverse 
of what it was when the piece R tended to turn faster than the 
piece C. The starting motor is now running idle and may be stopped 
without interfering in any way with the operation of the engine. 

In some cases a double overrunning clutch is employed as 
shown diagramniatically in Fig. 197. With a double combination 



Fig. 197— The double overrunning roller 
type clutch used by the Northeast com¬ 
pany 


272 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



of this kind the machine may be operated at one speed when 
acting as a motor and driving the engine and at another speed 
when it is being driven by the engine and acting as a generator. 

Overrunning Ratchet-and-Pawl Clutch 

The operation of the overrunning ratchet-and-pawl type of 
clutch may be understood easily by reference to Fig. 198. Four 
pawls are attached to a plate, which in turn is fastened to the 
crankshaft or shaft that is to be driven. These four pawls engage 
teeth cut in the inner periphery of a ring which is the driving 
portion of the clutch. One, or perhaps two, of the pawls will be 
engaged with the teeth when the engine is at rest, due to the action 


Fig. 198 —The operation of the overrunning 
ratchet and pawl type of clutch is explained ~by 
reference to this drawing 

of their counterweights. The two pawls marked A and B are 
engaged at the position shown in Fig. 198. Power is transmitted 
from the starting motor through the outer portion, or ring, to 
the plate on which the pawls are mounted as long as any one of 
the pawls is engaged with the teeth. Just as soon, however, as 
the speed of the plate exceeds that of the ring the pawls are dis- 






MOTOR AND ENGINE CONNECTION 


273 


engaged and held away from the teeth by the centrifugal force 
acting on their counterweight. To prevent the pawls from sud¬ 
denly re-engaging when the engine comes to a stop and rocks 
back and forth, a second set of pawls is provided, and they are 
shown at E, F, G and H in the figure. When the clutch is in¬ 
operative or idle all this second set of four pawls fall into their 
lowest position. Just as soon as the plate on which they are 
mounted rotates they are thrown out to a radial position, as 
shown by the position of the one marked H. If the plate happens 



Fig. 199— Friction clutch and worm-and-worm gear which connects 
Hartford starting motor to the engine 


to start to revolve in the opposite direction, the inertia of the 
four smaller pawls throws them into the position shown by the 
one marked G, which prevents the main pawls engaging the 
teeth. When the plate on which the pawls are mounted comes 
to a complete stop at least one of the main pawls will fall into 
a correct position for starting. 

Friction Clutch 

The Hartford starting motor is connected to the engine by a 
friction clutch and worm-and-worm gear as shown in Fig. 199. 
When the starting switch pedal is depressed the electrical con¬ 
nection between the motor and battery is completed, and at the 




























274 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


same time a strong pull is produced on the lever attached to the 
end of the rod P, which transmits a strong pull on the friction 
clutch mounted in the flywheel of the motor and thus connects 
the motor to the engine. 

Non-Automatic Pinion Shift 

The fundamental principle of the non-automatic pinion shift 
is shown in Fig. 200. When the switch rod is moved to the start¬ 
ing position it operates the switch and connects the motor to 
the battery and at the same time causes the sliding pinion to be¬ 
come engaged with the gear on the flywheel. The overrunning 
clutch mounted in the intermediate gears prevents the engine from 
running the starting motor at an excessive speed. Just as soon 
as the switch rod is restored to its normal position both the start- 



Fig. 200 —Drawing to illustrate fundamental principle 
of the non-automatic pinion shift 


ing switch and sliding pinion are restored to their normal posi¬ 
tion. 

Another good example of the non-automatic pinion shift is 
found in certain installations of the Westinghouse Electric & Mfg. 













MOTOR AND ENGINE CONNECTION 275 

Co., shown diagrainmatically in Fig. 201. In the non-automatic 
mechanical pinion shift of the Westinghouse company, a starting 
pedal is mounted on the foot-board, or a lever is mounted con¬ 
veniently for hand operation. The operation of the system thus 
controlled can best be understood by reference to Fig. 201. The 
contact-making part of the switch is shown in this diagram 
mounted on the gear-shift rod. 

At A is the “off” position of the shift pinion and switch con¬ 
tactor. Pressure on the starting lever moves the shift rod first 



Fig. 201 —Westinghouse system—A gives the “off” 
position of the shift pinion and switch contactor; 
in B the motor circuit is closed and the motor 
starts at low speed 

to the position shown in B, closing the motor circuit at P and P t 
through the resistance R; this starts the motor at low speed. 
Further motion of the shift rod to position C opens the electric 
circuit, but the motor and pinion continue to turn, owing to their 
momentum. When the position C is reached, the pinion still is 
turning slowly so that it cannot fail to mesh with the gear; but 












































276 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

as power is turned off the motor, there is no difficulty in sliding 
the teeth into full engagement. As soon as the teeth do engage, 
further foot pressure on the starting lever shifts the rod to the 
position shown in D, closing the electric circuit at Q after the 
pinion and gear have meshed a sufficient distance to present a good 
bearing length on the teeth. This connects the motor directly to 
the storage battery so that full power is impressed, turns over the 
engine until the starting lever is released or the engine picks up 
on its own power. There is an over-running clutch between the 



Fig. 201 —At G the teeth can be slid into full en¬ 
gagement, after which the motor connects directly 
with the storage battery and the engine is turned 
over } D 

flywheel pinion and the motor, so that if the pedal is not promptly 
released when the engine picks up, the motor is not driven by 
the engine. When the pressure is removed from the starting lever, 
the shifting-rod springs return all parts to position A. This re- 











































MOTOR AND ENGINE CONNECTION 277 


leases the gears and opens the electric circuit, and the motor 
comes to rest. 

The pinion is meshed with the gear on the flywheel in the 




Fig. 202 —Bijur system—as applied to the 1916 Hupmobile 
— A, out of action, starting switch off, pinion against motor 
head; B, about to crank, gears have meshed, but switch has 
not made contact 

Bijur system as applied to the Hupp motor car by pressing the 
starting pedal, and by a further movement the starting switch is 
closed. Four stages in the operation of starting the engine aro 














































ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

shown in Fig. 202. No overrunning clutch of any kind is used in 
this particular system, and fon this reason the motor should be 




Fig. 202 — *C, cranking . note cap between collar on shifting 
rod and clevis pin—shifting fork is against stop, and shifter 
spring is compressed slightly. D, about to crank, when gears 
are not meshed, teeth are butting but switch has made con¬ 
tact. Shifter spring is compressed strongly, ready to draw 
pinion into mesh 


disconnected from the flywheel just as soon as possible after the 
engine starts to fire. 






















































279 


MOTOR AND ENGINE CONNECTION 

Automatic Electromagnetic Pinion Shift 

The starting motors the Westinghouse Electric & Mfg. Co. used 
in this application are composed of three principal parts; tne sta¬ 
tionary parts, or field; the rotating parts, or armature and shaft; 
and the shifting magnet. The armature is mounted on a hollow 
shaft; on the end of this shaft is mounted a splined pinion which 
drives the engine flywheel. The pinion is made to slide along the 
shaft by a shifting rod which is attached to the pinion and passes 
through the hollow shaft. The other end of this shifting rod acts 
as the core of the shifting magnet. When the motor is not re¬ 
volving, a return spring holds the pinion at the end of the shaft 
and clear of the flywheel gear. 

As shown diagrammatieally in Fig. 203, when the starting 
switch is closed a circuit is complete from the negative terminal 
of the battery through the switch, the shifting magnet, the arma- 



Fig. 203 —Here the closing of the starting switch com¬ 
pletes a circuit between the terminals of the switch 


ture and the series field of the motor to the frame of the car and 
through this to the positive terminal of the battery. The motors 
used in this application are of the series type; that is, the field 
is connected in series with the armature so that all the current 
flowing through the one also flows through the other. One of the 
characteristics of this kind of motor is that the amount of cur¬ 
rent flowing through it is proportional to the amount of energy 
it develops. 

When the starting switch is closed, current flows through the 
circuit as noted above, causing the armature and shaft and the 
pinion to rotate. The motor requires a high current at the instant 
it starts from rest. This high current, through the shifting mag- 








280 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

net, energizes it sufficiently to overcome the force of the return 
spring and therefore draws the shifting rod through the shaft, 
thus sliding the pinion into mesh with the gears on the flywheel. 
The teeth on the flywheel and the pinion are cut diagonally so 
that they mesh very easily. As soon as the pinion meshes with 
the flywheel gear, the current required to turn the engine over 
is enough to hold the pinion in mesh until the engine fires. When 
the engine picks up it soon runs at higher speed than that of the 
motor. 

When the engine speeds up so that its speed approaches the no- 
load speed of the motor, the current in the latter falls off so that 
the pull of the shifting magnet is less than that of the return 
spring, which therefore throws the pinion to its original position 
clear of the flywheel. The motor will continue to revolve, without 
load, however, until the starting switch is opened or released; but 
the pinion remains out of mesh, because the current required to 
turn over the motor is not enough to energize the shifting magnet 
sufficiently to pull the pinion back into mesh against the force 
of the return spring. 

Bendix Drive, or Automatic Pinion Shift 

The Bendix drive consists of a solid or hollow shaft having 
screw threads on the outside and a hollow gear having screw 
threads on the inside, so that the gear screws on the shaft like 
a nut on a bolt. A circular weight is fastened to the gear and is 
slightly out of balance. A coil spring connects the electric motor 
shaft and the hollow screw shaft. The relation of these various 
parts is shown in Fig. 204. 

When the electric motor starts, it drives through the spring and 
turns the screw shaft. Because of the weight the gear is too heavy 
to turn with the screw shaft, and because the gear does not turn 
it must move along the screw shaft, just the same as if you turned 
a bolt having a nut on it and kept holding the nut with your fingers 
to keep it from turning so that it would be screwed along the bolt. 
After the screw gear has moved along the screw shaft and engages 
with the flywheel gear, it then keeps on moving along until it reaches 
the stop at the end of the screw shaft. The two gears then are fully 
meshed, and when the screw gear has reached the stop it must turn 
with the screw shaft. At this moment the screw shaft and electric 
motor are revolving at a great speed, and this great blow and the 


MOTOR AND ENGINE CONNECTION 281 

power of the electric motor both are taken through the coil spring. 
The spring keeps coiling until all this power has been applied to the 
flywheel gear and the engine starts turning. 

As soon as the engine starts exploding and runs under its own 
power, the flywheel turns much faster than when it was cranked 
by the starter. Because it is now turning so much faster it increases 
the speed of the screw gear, so that the latter runs faster than the 
screw shaft on which it is mounted. Therefore, when the screw 
gear runs faster than the screw shaft, it is screwed on the threads of 
the shaft, like a nut on a bolt, until it has been screwed out of mesh 
with the flywheel gear. This de-meshing movement is entirely auto¬ 
matic and eliminates the use of an over-running clutch. Now that 
the screw gear is out of mesh, it is natural to suppose that if the 
electric motor keeps running, the gear automatically will be 
screwed right back into mesh with the flywheel gear. But the un¬ 
balanced weight on the screw gear now performs its automatic 
function, that is, being slightly out of balance, the weight twists 
or cocks the screw gear so that it clutches and binds on the screw 
shaft and turns with it. This automatic clutching is due to the 
centrifugal force of the unbalanced weight. When the electric 
motor stops running the screw gear has been fully screwed away 
from the flywheel gear, and it remains in that retarded position 
until it is required to start the engine. 

The gear on the screw shaft has an automatic self-cleaning action, 
but, in any extreme case, should the gear tend to stick on the shaft, 
through being covered with mud, it may be necessary to clean the 
screw. 

The teeth on the screw gear and flywheel are chamfered, or 
pointed, on only one side to make the meshing natural and easy. 
However, should the teeth meet, end to end, the screw shaft itself is 
designed to move backward automatically and compress the coil 
spring. This gives the screw gear time enough to turn and enter 
the flywheel gear. Should sticking of gears ever occur, they can 
be released by throwing in the clutch and moving the car. Such 
trouble would be due to incorrect chamfering or inaccurate align¬ 
ment of the gears. Also it might be due to the binding of the drive 
parts and prevent compressing and proper functioning. 

If, while the engine is running, the electric motor should be 
started accidentally, the screw gear will screw over against the 
turning flywheel gear. But instead of the clashing and smashing 


282 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



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£ 

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as applied to Remy motor 









2b3 


MOTOR AND ENGINE CONNECTION 

of gears that might be expected there is no danger whatever, as the 
gears simply touch once. This is because the flywheel gear will 
speed up the screw gear, and thus automatically screw it away. 
The turning screw gear will then automatically clutch and bind on 
the screw shaft, in exactly the same manner as when it is cranking 
and has been de-meshed when the engine starts exploding. 

Old Bosch-Rushmore Electromagnetic Drive 

The starter drive used on the old Rushmore system, which 
was acquired by the Bosch Magneto Co., and later known as the 
Bosch-Rushmore system, is a feature of the later Bosch products 



Fig. 205 —Sectional view of old Bosch-Rushmore starter. It is 
still a feature of Bosch products but has been improved 
decidedly 


with decided improvements. The old Rushmore drive is illustrated 
and described herewith. The Bosch improvements will be taken 
up later. 

The construction of the Bosch-Rushmore motor is such that the 
armature can be shifted endwise in its bearings. In the non¬ 
operating position the armature is held out of its electrical center 
or, in other words, out of line with the pole shoes, by a spiral spring 
in the commutator end of the armature shaft; therefore, when in 
the normal position, the pinion on the driving shaft of the starting 
motor is out of mesh with the gear ring on the flywheel of the 
engine. A sectional view of the motor is shown in Fig. 205. 

The motor is provided regularly with three terminals, two of 
which are heavier, or of larger diameter, than the other. The two 
heavier terminals are for the main circuit, and the single small 
terminal is for the shunt circuit. 





284 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


During the first part of the downward movement of the switch 
pedal an electrical circuit is established, which causes the current 
from the battery to pass through the switch shunt. The amount of 
current that can flow is limited by the resistance of the circuit, but 
of the current which passes through the switch shunt a small portion 
is allowed to flow through the motor armature, while the greater 



Fig. 206 —Electrical circuit of Bosch system 
with switch pedal in first part of 
dowmcard movement 


portion flows through the motor field coils, forming thereof a strong 
electromagnet. See diagrams of electrical circuits as given in Figs. 
206 and 207. The result is a powerful attraction between the field 
coils and the armature, causing the latter to be drawn endwise 
into the magnetic center of the motor or, in other words, into its 



Fig. 207 —Here the switch pedal has com¬ 
pleted the downward movement and the 
engine turns over 


working position between the pole shoes. The passing of the small 
current through the armature causes the armature to rotate slowly, 
and as the rotary motion occurs simultaneously with the shifting of 
the armature endwise, the meshing of the motor pinion with the gear 
ring on the engine flywheel is accomplished quickly and positively. 

As the switch pedal reaches its limit of motion the flow of battery 
current through the switch shunt, as well as that through the shunt 
cable to the field coils, is interrupted, and a straight series motor 
connection is established, allowing the entire current to pass through 
the motor field and armature windings and causing the engine to 












MOTOR AND ENGINE CONNECTION 


285 


turn over until it starts firing. Although it takes time to explain 
this series of actions, the entire operation takes place so rapidly 
that the impression on the observer is that the motor pinion slips 
into place and begins turning the engine flywheel immediately after 
the starting switch pedal is depressed. 

As soon as the engine starts the starting motor is relieved of its 
load, and the current passing through it drops rapidly in volume, 



Fig. 208 —<Armature of Bosch starting 
motor in non-operating position 


this being a characteristic of series motors. In consequence, the 
strength of the field magnets is lessened to a point where the spiral 
spring in the end of the armature shaft overcomes the magnetic 
attraction holding the armature and returns it to the original, or 
non-operating, position. It is this action that automatically and 
positively throws the armature shaft pinion out of mesh with the 
flywheel gear ring. Thereafter, until the starting switch is released, 



Fig. 209 —Armature of Bosch starting 
motor in operating position 


any current which continues to pass through the armature merely 
will cause the latter to devolve freely but without meshing with the 
flywheel, due to the fact that the amount of current utilized when 
the motor is running free is not sufficient to overcome the tension of 
the spiral spring. The non-operating position of the armature is 
shown in Fig. 208 and the operating position in Fig. 209. 
































28G ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Direct Application of Starting Motor 

The combined motor and generator used in the system manufac¬ 
tured by the United States Light & Heating Co. differs from any 
of the other systems which are designed primarily for starting and 
lighting systems in that the device is incorporated in the flywheel 
housing, and the revolving part is mounted directly on the end of 
the engine crank shaft without any reduction gears or chains of any 


Fig. 210 —Component parts of U. 8. L. system. A combined 
motor and generator is used in this system 

kind. The component parts of the system are shown in Fig. 210. 
A section through an assembled system is shown in Fig. 211, in 
which the parts shown in shaded areas are to be furnished by the 
U. S. L. company and parts shown in white, or section, are to be 
furnished by the manufacturer of the car. The field is of the mul¬ 
tipolar construction and it is held rigidly in position by bolts in the 
front of the flywheel compartment. The armature, or rotor, is 


MOTOR AND ENGINE CONNECTION 


287 


mounted on a special flange fastened to the back end of the engine 
crankshaft, and it revolves outside the field structure. In some 
types of U. S. L. systems the armature revolves inside the field 
structure. 


Back-Kick Releases 

The object of a back-kick release is to take care of any excessive 
strain which may be put on the device used in connecting the motor 
to the engine. If the spark lever be too far advanced, there will 
be a premature explosion, which will tend to rotate the motor in 
the opposite direction to that in which it is running and thus subject 
the connecting device to a very severe strain. The power of the 
motor is ample to overcome this strain in the majority of cases, and 
the connecting devices are designed with this abnormal condition in 
ir.ind, and as a result the necessity of any special device is not nearly 
so great as it might at first appear. 

A device used by the Northeast company consists of a friction 
clutch which is held in contact by springs. This clutch will not slip 
under ordinary and reasonable loads, but should the load become 
unusually excessive it will slip and thus protect the remainder of 
the connecting equipment between the motor and the generator. 

A friction clutch is used on the Hartford starter on account of 
the irreversible worm-and-worm gear drive used, as the teeth of the 
gear would more than likely be damaged in case the engine back¬ 
fired. 

A brake band is sometimes used in combination with the starting 
gears, and this band is held tight, in such a manner that it holds 
and transmits power in one direction only. 


Location of Starting Motors 

A number of different possible locations of the starting motor 
with reference to the engine and transmission are shown in Fig. 212. 

The shaft of the motor, as shown at 1, is at right angles to 
the crankshaft of the engine and usually is connected to the 
crankshaft by a worm-and-worm gear alone or a worm-and-worm 
gear in combination with a second gear or chain. An example of 


288 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


INSTRUMENT BOARD 


TERMINAL BLOCK 
AND STARTING^ 
SWITCH 



FIELD OR 
STATIONARY PARTS 


Fig. 211 —Section through assembled V. S. L. system. The parts 
shown in white are furnished by the maker of the car; those 
in shaded areas, by the U. S. L. company 













































































































MOTOn AND ENGINE CONNECTION 289 

the location of the motor m which the connection is by a worm- 
and-worm gear was shown in Pig. 199. 

The motor may be located alongside the engine as shown at 2 
in Fig. 212 and connected to the crankshaft by gears or a chain 
or perhaps a combination of the two. An example of this loca¬ 
tion of the motor in which the connection is made by a chain is 
shown in Fig. 213. 

The starting motor may be mounted in front of the flywheel 
as shown at 4 in Fig. 212 or it may be located behind the fly¬ 
wheel as shown at 5 in the same figure. In the majority of cases 
the connection is direct between the pinion on the motor and a 
gear cut in the surface of the flywheel or in a collar which is 
mounted on the rim of the flywheel. In some cases a chain or 
gear reduction is introduced between the motor shaft and the 



Fig. 212 —Diagram to illustrate possibilities of starting motor 
location icith reference to the engine and transmission 


gear on the flywheel. The pinion on the driving shaft may be 
made to engage the gear on the flywheel by any one of the several 
methods previously described. Installation of a double-deck ar¬ 
rangement of motcr and generator in the Saxon four is shown in 
Fig. 214. The installation of the Bijur system on the Packard is 
shown in Fig. 215. 

The application of the Bosch flywheel starter to the Marmon is 
shown in Fig. 216. The pinion in this system is made to mesh 
with the gear on the flywheel by moving the shaft on which the 
pinion is mounted endwise. This movement is produced by the 
magnetic pull of the field of the motor on its armature which is 
normally off center with respect to the field as shown in section 
in Fig. 205. 

The installation of a Westinghouse starting motor on the 
Chalmers six is shown in Fig. 217. The motor in this installation 
is mounted on the gear case and a bearing is provided in the fly- 
















































290 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

wheel case for the end of the shaft on which the pinion is mounted. 

A representative starting motor as made by the Delco com¬ 
pany for direct flywheel drive is shown in Fig. 218. 

The method of connecting the motor, shown at 6 in Fig. 212, 
is decidedly different from any of the other methods thus far 
described in that it is connected to the transmission shaft, and 
power is transmitted from the motor to the engine through the 
friction clutch in the flywheel. An installation of this kind is 



Fig. 213— Application of dynamotor made 
fty the Dyneto company to the Franklin 
engine 


found on the Reo car, it being manufactured by the Remy com¬ 
pany. 

The only example of the motor installation shown at 7 in Fig. 
212 in which the electrical unit is installed for starting and gen¬ 
erating purposes alone is that of the U. S. L. system. An example 
of the complete installation of this system is shown in Fig. 219. 

Purpose of Generator Drive 

The function of the generator is to provide a suitable means of 
charging the storage battery while it is installed on the motor 


MOTOR AND ENGINE CONNECTION 


291 



Fig 214 —Installation of double-deck arrangement of motor 
and generator in the Saxon four 



Fig. 215 —Installation of Bijur system on the Packard 
car, thus keeping the battery practically completely charged 
at all times so that an ample supply of energy is always available 
for operating the starting motor, lamps, horn and other electrical 














292 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 216 —Application of the Bosch flywheel starter to the 
Marmon 



Fig . 217 —Installation of a Westinghouse starting motor on 
the Chalmers six 

devices which may be installed originally on the car. In no case 
should additional electrical equipment be installed upon any car 
unless you are reasonably sure the capacity of the storage bat- 

















MOTOR AND ENGINE CONNECTION 293 

tery is ample to take care of the additional load and at the same 
time the capacity of the generator is sufficient to keep the battery 
charged under normal operating conditions. 

The generator will not start to charge the storage battery until 
the electrical pressure generated in its armature is greater in 
value than the electrical pressure of the battery. The electrical 
pressure generated in the armature winding of the generator 
depends on the speed at which the generator is driven, and it 
will vary directly as the speed at which the armature is revolved 
if all the other quantities on which the pressure depends, such 
as the strength of the magnetic field of the machine, etc., remain 



Fig. 218 —Delco motor for attachment to flywheel case 


constant in value. It is obvious, since the electrical pressure in 
the armature of the generator depends on the speed, that the 
battery would discharge back through the generator, if they 
were permanently connected together, when the speed of the 
generator happened to be of such a value that the electrical 
pressure of the generator was less than the pressure of the 
battery. The function of the cutout is to provide a means of 
disconnecting the battery from the generator when the battery 
starts to discharge back through the generator. As explained in 


294 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

one of the previous chapters, these cutouts assume several different 
forms, some being operated electrically and some by hand. 

In order that the electrical pressure in the armature winding of 
the generator may increase in value as the engine speeds up and 
the generator starts charging the battery, it is necessary that 
some mechanical connection be established between the crank¬ 
shaft of the engine and the armature shaft of the generator. The 
requirements of this connection are quite different from those 
imposed on the mechanical connection between the starting motor 



Fig. 219 —Complete installation of U. S. L. 
dynamotor 


and the crankshaft of the engine. First of all, the torque re¬ 
quired to drive the generator when it is delivering its rated or 
normal full load will be nothing like as great as the torque the 
starting motor must develop when it is turning the engine over 
in starting; hence, the mechanical strains to which the generator 
connections are subjected will as a rule be less than those im¬ 
posed on the motor connections. Second, the design and opera¬ 
tion of the motor connection in the majority of cases must be 
such that the motor will be disconnected from the engine crank¬ 
shaft when the engine starts to fire either automatically or by 



MOTOR AND ENGINE CONNECTION 


295 


some manual means. No such requirements need be met in the 
case of the generator connection, and they are connected in almost 
every case permanently to the crankshaft of the engine. In some 
cases, such as in the installation of the Delco dynamotor, a double 
mechanical connection is provided, but its construction is such 
that only one connection is operative at any one time as will be 
explained later. Third, the ratio between the speed of the gen- 



Fig. 220 —<Sectional view of one form of Gray & Davis 
friction drive, perpendicular to armature shaft 


erator shaft and the crankshaft of the engine, except in the case 
of dynamotors with a single drive, is quite different from the 
ratio between the speed of the motor shaft and the crankshaft 
of the engine. This difference is due chiefly to the fact that the 
generator will be connected to the engine all the time and, of 
course, will have to operate under a wider total variation in engine 
speed than the starting motor. 

If the same relation between engine and generator speed were 
provided as in the case of the motor, the speed of the generator 
would exceed the allowable limit, and it would be almost impos¬ 
sible to construct an armature and commutator that would with- 























296 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

stand continuously the enormous centrifugal forces that would 
exist at these very high speeds. In the connection of a dynamotor 
to the engine by a single drive, the gear ratio will have to be 
lower than the maximum ratio with a double drive to keep the 
maximum speed down. Fourth, in some cases the ignition dis¬ 
tributor is combined with the generator and driven through a 
gear connection from the generator shaft. In such cases it is 
absolutely imperative that the position of the distributor arm in 



Fig. 221 —Sectional view of another form of Gray & Davis 
friction drive, parallel to armature 


relation to the proper firing order of the various cylinders remain 
fixed at all times, and in such cases it is obvious that the con¬ 
nection between the generator and the engine must be very 
definite. 

Generator connections may be divided into the following main 
groups and a brief description of one or more typical examples 
of each kind will be given: 

Friction drive. 

Belt drive. 

Chain drive. 

Gear drive. 

Mounted directly on engine shaft. 

Friction Drive for Generator 

A sectional view of the friction drive as used by Gray & Davis 
on their types E and G-l generators is shown in Fig. 220, and 




















































MOTOR AND ENGINE CONNECTION 297 

a sectional view parallel to the shaft of the generator is shown in 
Fig. 221. The cup-shaped piece of metal marked 1 in both figures 
is connected to the end of the driving shaft. Two friction shoes, 
marked 3, are connected mechanically to the end of the generator 
shaft, so that they may move in or out along pins in the end of 


Fig. 222— Belt-driven generator as installed on a Ferro eight- 
cylinder engine 

the shaft, and are held against the inside surface of the cup 1 by 
coiled springs, 2, which are under compression. Two weights, 
marked 4, are connected mechanically by four links to the fric¬ 
tion shoes. These weights may move perpendicularly to the shaft 
along pins fastened to the shaft which enter holes in the weights. 


298 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


As the speed of the driving shaft increases, the centrifugal force 
acting on the weights increases, and this action tends to draw 
the two friction clutches away from the inside surface of the 



Fig. 223 —Chain drive in which the chain is inclosed as 
installed on a Colonial eight 

cup and thus disconnect the generator shaft from the driving 
shaft. In the majority of cases, when the generator is driven, 
the speed of the generator shaft at which the disconnection 
actually takes place will depend on the adjustment of the two 
coil springs holding the weights against the inside of the cup. 






MOTOR AND ENGINE CONNECTION 299 

These springs may be adjusted by inserting a small screw driver 
in the opening 5. When the maximum current output of the 
generator is to be increased, which amounts to increasing the 
speed at which the generator shaft is driven by the driving shaft, 


Fig. 224 —A Splitdorf-Apelco dynamotor as originally installed 
in a Ford } showing a chain drive in which the chain is exposed 

the screw in the opening 5 should be turned to the right. The 
governor is very sensitive, and only a slight movement of this 
adjusting screw is necessary to produce a decided difference in 
the output of the generator. Just as soon as the speed of the 
generator decreases a slight amount after the friction shoes are 
raised from contact with the inside surface of the cup, the cen¬ 
trifugal force acting on the weights will decrease, and the springs 
will shove the shoes out against the cup and again establish the 





300 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

mechanical connection between the generator and the driving 
shaft. The total variation in the speed of the generator, when 
the speed of the driving shaft exceeds the speed for which the 
generator is adjusted, does not amount to very much, and as a 
result the electrical pressure generated in the armature winding 
will rise to a certain maximum value and then remain practically 
constant for all higher engine speeds. 

The small projections around the outer surface of the cup 1 
produce a fan-like action which causes a circulation of air through 



Fig. 225 —Installation of gear-driven generator on the Amal¬ 
gamated engine 


the generator, thus tending to keep its temperature lower than 
it would otherwise be. 

Belt Drive for Generator 

The generator may be driven by a small belt which runs over 
a small pulley connected directly on the engine shaft, or the 
pulley may be connected to the pump or timing gear shaft. In 
some cases the belt used in operating the cooling fan for the engine 
is increased in length and made to travel around a small pulley 
mounted on the end of the generator shaft. Care must be exer¬ 
cised in this particular type of drive to be sure that the belt is 
always tight enough to prevent an undue amount of slipping. 
Some special means usually is provided for taking up a reasonable 
amount of slack in the belt by moving one of the pulleys over 
which the belt runs or providing an idle pulley whose position 



MOTOR AND ENGINE CONNECTION 


301 


may be changed as conditions demand. An example of a belt 
drive is shown in Fig. 222, which depicts a belt-driven generator 
as installed on a Ferro eight-cylinder engine. 

Chain Drive for Charging Generator 

The chain drive has several advantages not possessed by the 
belt drive, and some of the more important ones are as follows: A 



Fig. 226 —Gearing of Gray & Davis double 
unit outfit for the Ford 


positive connection between the generator and the engine at all 
times; no stretching and hence no special attention is necessary 
to keep it in adjustment; it may be inclosed and thus better pro¬ 
tected and at the same time easily lubricated. Such a drive is 
the short chain at the left of Fig. 223, which is a Colonial eight. 


302 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


All chain drives, however, are not inclosed, especially the earlier 
installations. An example of a chain drive in which the chain 
is exposed is shown in Fig. 224, which depicts a Splitdorf-Apelco 
dynamotor as originally installed on a Ford car. 

Gear Drive for Charging Generators 

The gear drive provides, as in the case of the chain drive, a 
positive connection between the generator and the engine crank¬ 
shaft. In the majority of cases, when the generator is driven 



Fig. 227 —Heinse equipment for Ford, in 
which the primary drive is by chain 

by gears, use is made of the timing or pump gears and the gen¬ 
erator directly connected to the end of a shaft on which these 
gears are mounted or to one of the shafts through a gear mounted 
on the generator shaft. The installation of a gear-driven gen¬ 
erator on a new engine design is shown in Fig. 225. The small 
gear at the bottom is on the generator drive shaft. 

Mounted Directly on Engine Shaft 

The best example of this particular type of installation is tliat 
of the U.S.L. system in which the generator and motor are com- 









MOTOR AND ENGINE CONNECTION 303 

bmed in a single unit and mounted in the fly-wheel housing in 
place of the flywheel itself. 


Combined Generator and Motor Drives 

The generator and motor drives may be one and the same drive. 
In some cases there are two drives between the dynamotor and 
the engine, the gear ratio of the two being different. One of these 
drives will transmit power from the dynamotor to the engine while 
the armature of the dynamotor tends to run, due to a motor action, 
ahead of the engine and is used in starting the engine. The other 
drive will transmit power from the engine to the dynamotor when 
the engine tends to run ahead of the armature of the dynamotor. 
In some cases a part of the connection will be used in transmitting 
power from the armature of the dynamotor and also in transmitting 
power in the opposite direction. In such a case an intermediate 
gear or sprocket is connected to the shaft of the dynamotor through 
a double roller clutch a part of which will drive in one direction 
and the other part in the opposite direction. An example of this 
type is shown in Fig. 226, which shows the gearing of the Gray & 
Davis double unit outfit for the Ford. The armatures are connected 
by a large gear and Bendix pinion. The latter becomes inoperative 
when the motor circuit is opened. A similar installation in which 
the primary drive is by chain is the Heinze equipment for Fords 
illustrated in Fig. 227. 


Gear Housings 

Gear housings are of numerous, different forms, ranging from 
a very open or exposed type to the completely inclosed type. In 
some cases this housing is provided by the engine manufacturer 
with the definite requirements of a particular starting and lighting 
system in mind, and in such cases the completed installation has a 
very compact and finished appearance. In other cases the gear 
housings are provided by the manufacturer of the electrical equip¬ 
ment and so designed that they may be readily mounted on the 
engine. No general rule is followed in this connection, which 
results in a very wide variation in the appearance and construction 
of the various different systems. An example of an inclosed type 
if motor, or generator, gear housing is shown in Fig. 228. 



304 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Gear Reductions 

There are quite a number of different methods of bringing 
about the proper speed relation between the motor and generator 
and the engine. This may be accomplished by a belt, by chain 
alone or in combination with gears, by a worm-and-worm gear, 
by the ordinary spur gear, by a planetary gear, etc. 

A gear reduction in which the gearing is supplied by the manu¬ 
facturer of the electrical equipment is shown in Fig. 229.' 

The gear reduction shown in Fig. 230 is used by the Westing- 
house Electrical & Mfg. Co. The small pinion on the end of the 
armature shaft meshes with three gears mounted on studs carried 


Fig. 228 —Inclosed gear housing as used with the North East 
system on a Dodge Bros, car 

on a plate, which in turn is mounted on a shaft extending through 
the end of the motor housing. The three gears also mesh with 
teeth cut on the inside surface of the motor housing as shown in 
the figure. When the pinion on the end of the motor shaft rotates 
it causes the three gears to rotate and they in turn travel around 
the inside of the motor housing, carrying the plate on which they 
are mounted with them, and hence the shaft extending through the 
motor housing will rotate, but at a much lower speed than the 
shaft of the motor. 










MOTOR AND ENGINE CONNECTION 


305 


A somewhat similar construction to the preceding is employed 
by the Wagner company, and an exploded view of their connection 
is shown in Fig. 231. The construction of this device is such that 
power is transmitted from the starting motor to the engine 
through the planetary gears when a brake band controlled by a lever 
on top of the starting motor holds the gear housing stationary. 
The complete device is shown in Fig. 232. When the gear hous¬ 
ing is free to turn and the engine speeds up the armature of the 
dynamotor is driven by the overrunning roller clutch. This com- 



Fig. 229 —Gear reduction in which the gearing is supplied by the 
maker of the electrical equipment 


bination allows the armature to operate at a higher speed in re¬ 
lation to the engine speed when the dynamotor is acting as a motor 
than it does when the dynamotor is being driven by the engine or 
when the dynamotor is acting as a generator 

Starting, Lighting and Ignition 

The complete electrical equipment of the modern motor car 
ordinarily included the three functions, starting, lighting and 
ignition.. To consider the equipment as a whole, all three func¬ 
tions must be taken into consideration, though in a great many in¬ 
stallations the ignition function either is quite separate or nearly 
so from the other two functions. 

Relation Between Functions 

The equipment by which the starting, lighting and ignition func¬ 
tions are maintained is arranged in different ways, and it is on 
the arrangements that the first general classification of all systems 
is based, and the design of the different unit? depends on which 



806 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


of the arrangements is employed. The electrical equipment which 
performs the ignition, lighting and starting of the motor car con¬ 
sists of the following main pieces of apparatus: 

First, for the ignition there must be a source of electrical 
energy, either a storage battery, dry battery, the familiar type of 
magneto generator or a generator which is not of the magneto 
type. In addition there must be means for transforming the low 
voltage current into a high voltage or high tension current and 
other means for distributing the current to the proper spark plug 
at the proper time. 

Second, for lighting there must be a source of energy, such 
as a storage battery, which may be used in operating the lamps 



Fig. 230 —Gear reduction used on West- 
inghouse starting motors 



Fig. 231 —Exploded view of Wagner gear 
connecting dynamotor to the engine 


and signalling apparatus, and a generator which is equipped with 
the proper regulating devices and cutout so as to keep the battery 
fully charged. 

Third, for starting the engine there must be an electric motor 
connected mechanically to the gasoline engine and connected 
electrically to the storage battery through the proper switches 


MOTOR AND ENGINE CONNECTION 


307 


so that the battery will produce an electric current in the wind¬ 
ings of the motor, causing its armature to revolve with sufficient 
force to turn the engine crankshaft over at the desired speed for 
starting. The battery producing the current to the windings 
of the motor must, of course, be charged in order that the battery 
be ready to meet any reasonable demands of the starting motor. 

It is evident that the equipment required in performing any one 
of the above three functions need not be entirely independent 
of the equipment required in either or both of the other two. 
For example, the same storage battery and charging generator 
which supply energy for lighting the car may be used in produc¬ 
ing current in the winding of the starting motor and, in many 
instances, for the ignition. Also, it has been found that other 
combinations of the equipment required in performing the above 



Fig. 232 —Complete Wagner dynamotor, an exploded view of whose 
connection was shown in the preceding figure 

three functions may be made for the sake of lightness and sim¬ 
plicity. 

There are, however, three fundamental parts to each system, 
no matter how the equipment required for these various functions 
may be interrelated, the ignition device, the charging generator 
and the starting motor. The manner in which these fundamental 
parts are related affords a means of classifying all starting, light¬ 
ing and ignition systems into three classes—three-unit systems, 
two-unit systems and single-unit systems. 




308 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


Difference in Names 

Many manufacturers of these systems disregard the ignition 
feature in the nomenclature of their apparatus so far as the types 
of systems are concerned. Thus, they consider only two systems, 
the single-unit and the two-unit. The former comprises the type 
in which generator and motor are combined and the latter the 
type in which the generator and motor are separate. The ignition 
may or may not be separate and does not affect their nomenclature. 
Since the ignition is a part of the electrical equipment frequently 
used in combination with the generator, the division into one-, 


Fig. 233 —Units of the three systems 



Single-unit motor-generator Two-unit motor with gener¬ 

ator and ignition separate 



Three-unit , a motor , a generator and ignition 

two- and three-unit types is considered the more logical. The units 
of the three systems are illustrated in Fig. 233. 

Three-Unit Systems 

The three-unit system is one in which the starting motor, the 
charging generator and the ignition device are separate machines, 
their only interconnections being to the* common storage battery, 
though in some systems of ignition, where magneto alone is used. 


















MOTOR AND ENGINE CONNECTION 


309 


the ignition has no connection at all with the other electrical 
equipment. The component parts of a three-unit system in which 
the starting motor, generator and magneto are distinct is shown 
in Fig. 234. The illustration explains how the units receive power 
from, or deliver power to, the crankshaft of the engine. 

Two-Unit Systems 

Two-unit systems are those in which any two of the three func¬ 
tions are taken care of by a single machine, leaving the remaining 
unit to take care of the third function. The generator which sup- 



SBU2K HOG 3 


Fig. 234 —Typical arrangement three-unit system, showing the 
mechanical and electrical connections of the separate units, the 
cranking motor, lighting generator and ignition magneto 

plies current to the battery may be fitted with an induction coil, 
contact breaker and distributor, so that it performs all of the func¬ 
tions of the ignition magneto and at the same time charges the 
storage battery. This leaves the cranking to be taken care of by 
a separate motor. Fig. 235 shows how the charging generator 
and ignition equipment are combined in a single unit, the starting 
motor being entirely separate, with the exception of its electrical 
connection to the same storage battery as the combined generator- 
ignition unit. Fig. 236 illustrates another design of this com¬ 
bination. 

In some types of two-unit systems the starting motor and the 
generator are combined as a single unit, leaving the second unit 
















310 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 235 —One unit of a two-unit system. 
This is a combined lighting and ignition 
generator, the cranking apparatus being 
separate. The distributer is driven by a 
worm and vertical shaft 



Fig. 236 —A two-unit system similar to Fig. 235 except that the 
distributor is on a horizontal shaft 


to take care of the ignition. The ignition may be taken care of 
by a magneto, in which case the ignition is entirely independent 
of the motor and generator functions, or the ignition may be 





































































MOTOR AND ENGINE CONNECTION 


311 


taken care of by an induction coil which draws current from the 
same storage battery used in combination with the generator and 
motor. 

In two-unit systems the generator and motor are combined in 
a single unit in a number of different ways. Instead of having two 
separate machines, they may be combined in the same frame, but 
each have a distinct field and armature of its own. An example of 



Fig. 237— Double-deck arrangement of 
motor and generator in same frame 


a combination of motor and generator in the same frame is shown 
in Fig. 237. In reality this combination is in itself a two-unit 
system, as the generator and motor actions are entirely inde¬ 
pendent of each other. The type of construction shown in 
Fig. 237 is called the double-deck arrangement. 

Another method of combining the generator and motor actions 
is to provide two separate windings on the armature of the same 
machine, one winding being the generator winding and the other 





312 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


the motor winding. This combination of motor and generator 
in a single machine is called a dynamotor—sometimes, motor- 
generator. Each of the armature windings is provided with a 
separate commutator and brushes. A machine of this kind is 
shown diagrammatically in Fig. 238, both commutators in this 
particular case being on the same end of the armature. When 



Fig. 238 —Application of a dynamotor in a two-unit system. It 
has two separate windings 


operating as a motor the machines usually drive through a gear 
on the flywheel, intermediate gear, or by silent chain to the crank¬ 
shaft. When operating as a generator, the machine is usually 
driven by the timing gears or by means of a silent chain.. 

Single-Unit System 

Single-unit, or unit, systems are those in which the starting, 
lighting and ignition are all taken care of by the same machine. 










































MOTOR AND ENGINE CONNECTION 313 

This consists of a dynamotor which has a contact breaker, induc¬ 
tion coil and distributor fitted to its generator end. A complete 
system of this kind is shown diagrammatically in Fig. 239. 

General Classification of Systems as to Wiring 

There are three general systems employed for wiring a car, 



HORN BUTTON- 

HEADLIQHTS 
HEADLIGHTS - 
COWL 






DRV CELLS TOR 
RESERVE IGNITION 


Fig. 239 —Typical single, or one-unit, system 



Fig. 240— Single-wire, or grounded return, system 





















































































314 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 





43 

JF) 


as follows: The single wire or grounded return, the two-wire 
and the three-wire system, respectively. 



Fig. 241 —Remy single uAre, or ground return, system as applied 
to an Oakland 32 

































315 


VICTOR AND ENGINE CONNECTION 

In the single-wire or grounded-return system the various 
electrical circuits are completed by using the frame of the car 




as a part of the circuit, as shown diagrammatically in Fig. 240. 
A pictorial diagram of an actual installation of this kind is shown 
in Fig. 241. This is a Remy installation on an Oakland Model 32 
car. Great care should be exercised in making the electrical 
connection to the frame of the car to see that it is as perfect 
as possible and not likely to work loose or be affected by corro- 




































































316 ELECTRICAL equipment of the motor car 

sion due to moisture or acid fumes. In some systems the positive 
terminal of the battery is grounded, while in others it is the nega¬ 
tive terminal. 

In the two-wire system both sides of the electrical circuit are 
insulated from the frame of the car and the electrical circuits are 
completed by wires. Such a system is shown in Fig. 242. 

The three-wire system consists of three wires, one known as the 
neutral and arranged as shown diagrammatieally in Fig. 243. The 
middle, or neutral, wire divides the battery into two parts, and 
the lamps and other electrical equipment may be connected between 
either of the outside wires and the neutral or between the outside 
wires. When the lamps are connected as shown in Fig. 243, if the 



Fig. 244— Simms-Hiiff system, which is a multiple-voltage system 
in which the two battery sections are connected in series 

fuse blows on one side the lamps on the other side still remain 
lighted. A good example of an installation of this kind is found 
in certain types of the U. S. L. systems. In these installations 
the connections of the starting switch are such that the two sec¬ 
tions of the battery are in parallel when operating the starting 
motor and in series the remainder of the time. All the lamps are 
in parallel and connected to the two batteries in parallel when the 
starting motor is being operated. 
















































MOTOR AND ENGINE CONNECTION 


317 


Operating Voltage 

Starting, lighting and ignition systems may be classified accord¬ 
ing to the value of the operating voltage into two main groups as 
follows: Single voltage systems and multiple voltage systems. 


Single-Voltage Systems 

A single-voltage system, as its name indicates, is a system em¬ 
ploying a single voltage for all the electrical operations. The value 
ef this voltage, as used at the present time, is in the great majority 
cf cases either 6 volts or a multiple of 6 volts, sueh as 12, 18, etc. 
The selection of the value of 6 as a unit is due to the voltage 
required in operating the old battery ignition systems, when dry 
cells were used and the three storage cells seemed to give very 
satisfactory results when used to replace the dry cells. The ad¬ 
vancement made in the last few years in the manufacture of 
efficient low-voltage charging generators and motors has done a 
great deal toward making these lower voltages standard rather 
than the higher values as originally used. The filaments of the lower 
voltage lamps are more rugged than those of the higher-voltage 
ones of the same candlepower, which is in favor of the use of the 
lower-voltage system. The losses in the lower-voltage systems 
are apt to be quite a bit greater than in the higher-voltage systems, 
due to the fact that a higher current will be required for a given 
powter unless a larger size wire and larger switch contact areas 
be employed. 


Multiple-Voltage Systems 

Multiple voltage systems are those employing more than one 
voltage. In systems of this kind two voltages are usually em¬ 
ployed, one for charging the battery and then a higher voltage 
for operating the starting motor. In such systems the battery 
usually is split into two sections. These two sections normally 
are connected in parallel, and the voltage of the charging gen¬ 
erator is such that the battery may be charged while connected 
in this way. A change in connections usually is made at the 


318 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

starting switch when the starting motor is to be operated, which 
results in the two sections of the battery being connected in 
series, and the voltage applied to the starting motor is that of 
the two sections combined. A good example of a system of this 
kind is found in the Simms-Huff system, as shown in Fig. 244. 
The connections are shown diagrammatically in Figs. 245 and 246 
for the charging and starting position of the starting switch. 
In this system the generator and motor actions are combined in 
a single machine. 

In some of the earlier forms of Deleo equipment the battery 
was composed of twelve cells, which were connected in four groups 
of three cells each. These groups were connected in parallel while 
charging and in series for operating the starting motor by quite 
a complicated switch. These switches were mounted on the end 
of the battery box proper and alongside an ampere-hour meter. 


CHAPTER XVIII 


Switches and Protective Devices 

T HE purpose of a switch in any electrical circuit is to provide 
a means of controlling the operation of the circuit by 
opening and closing or completing the circuit just as a valve in 
a hydraulic circuit or pipe affords a means of opening and clos¬ 
ing the circuit of which the valve is a part. Electrical switches 
assume many different forms and sizes, depending upon the 



Fig. 245 —\The charging position of the starting switch, showing 
the connections at that position 



Fig . 246 —The starting position of the starting switch, showing the 
connections at that position 

service for which they are designed primarily, which places cer¬ 
tain requirements upon the switch in order that it operate suc¬ 
cessfully. Thus, a switch that is to carry a heavy current must 
be constructed with large contact surfaces in order that the resist¬ 
ance of these contacts be low; the surfaces of the materials which 
come into contact with each other must be smooth and should be 
in actual contact over as large an area as possible; the opera¬ 
tion of the switch should be as positive as possible, and all con¬ 
necting terminals and parts should be of ample size to meet the 










































320 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ordinary requirements to be imposed on the switch when in 
actual service. 

In a great many cases certain parts of the switch are made up 
of a number of thin pieces of copper instead of one single heavy 
piece. This construction gives much better contact and also a 
surer contact in the majority of cases. A switch of this kind 
is said to be laminated. The selection of the material to be used 
at the breaking points of the switch will depend upon how severe 
an arc is likely to form and the probable destruction or damage 
resulting from such an arc. The breaking contacts are in some 



Fig. 247 —Wiring diagram of Gray do Davis grounded system, illus¬ 
trating application of single-pole switches 


cases made of carbon, but in the great majority of cases metal 
is used. Switches that are to carry a small current, such as those 
ordinarily found in the lighting circuits of a motor car, are much 
smaller and require smaller contacts and smaller parts as a 
whole; but their operation should be quite positive to reduce 
the tendency for arcs to form at the points of contact when these 
contacts are being made and broken in the operation of the switch. 
If a switch is to be used in a high pressure circuit, such as the 
secondary circuit of an induction or ignition coil, it must be con¬ 
structed in such a manner and of such materials that it easily 
will stand the electrical pressure to which it will be subjected un¬ 
der all ordinary working conditions. The construction of any 
switch is influenced greatly by the location in which it is to be 
mounted and the manner to be employed in operating the switch. 




























SWITCHES AND PROTECTIVE DEVICES 321 

Quite often a switch is used to change the connection of the 
various elements of a circuit rather than to serve as a means 
merely of opening and closing the circuit. A good example of 
this requirement, as imposed upon a switch, is found in those sys¬ 
tems where the connections of the various sections of the battery 
are changed from a multiple connection while the batteries are 
being charged to a series connection when the batteries are being 
used in operating the starting motor.. In some cases a switch is 
introduced into a circuit merely for the purpose of reversing the 



Fig. 248 —Connections of two-pole rotary switch on the 1913 
Haynes car. The letters are for later reference 

connections of a certain part of the circuit with reference to some 
other part. Thus, in certain ignition systems we find what com¬ 
monly is called a polarity switch, its purpose being to reverse the 

. 

connections of the interrupter points with respect to the battery 
or generator in order that the wasting away of the two interrupter 
points may be equalized. If the direction of the current through 
an interrupter remains unchanged in direction, there will be 
quite a difference in the degree to which the two contact points 
are worn away. The metal naturally tends to travel in the direc¬ 
tion of the current, and as a result there is a much greater wasting 
away of the positive contact than there is of the negative con- 























3£2 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

«> 



Fig. 249 —Here is a common form of the single-pole blade switch 



Fig. 250 —Interior mechanism of two-pole snap switch 


















SWITCHES AND PROTECTIVE DEVICES 323 

tact. An inspection of a set of contacts that have been in service 
for some time will convince you of this fact. 

Single and Multipole Switches 

A single-pole switch is one in which provision is made for open¬ 
ing the electrical circuit in which the switch is connected at one 
point, oidy. An example of a switch of this kind is shown diagram- 
matically in Fig. 247. The positive terminal of the battery is 
grounded in this case, and the starting motor and its series field 
winding are connected permanently in series to the positive or 



Fig. 251 —The rotating, or drum, switch, used hy 
the Leece-Neville Co. 


grounded terminal of the battery. The starting switch is intro¬ 
duced in the lead connecting the negative terminal of the battery 
and one terminal of the armature of the starting motor. The 
lighting switches in this figure are also single-pole, and their 
connections are very similar to 1 those of the starting switch. 
Current for the lights flows through the series field of the genera¬ 
tor and serves to raise its voltage, which increases its output the 
required amount to take care of the lamps when they are 
turned on. 

A two-pole switch is one provided with two sets of contacts. 
Two-pole switches may be so connected that one set of contacts 
is introduced in one circuit and the remaining set in another cir¬ 
cuit, which really amounts to two single-pole switches mechan- 




















324 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ically connected together, and both circuits are operated at the 
same time. In the great majority of cases, however, the two 
sets of contacts of a two-pole switch are introduced in the same 
circuit, one set being introduced in one side of the line and re 
maining set in the opposite side of the line. A good example of 
a two-pole switch is shown diagrammatically in Fig. 248, which 


Q 



Fig. 252 —The rotating, or drum, switch 
used by the Wagner Electric Co. 


represents the connections of the rotating starting switch on 
the 1913 Haynes car. 

Multipole switches are those having more than a single set of 
contacts. A very good example of a multipole switch is found 
in early models of the Delco systems, in which the switch was 
used for connecting four sections of a storage battery in parallel 
for charging and in series for operating the starting motor. 







































SWITCHES AND PROTECTIVE DEVICES 


325 


Kinds of Switches 

A blade switch is one in which the connection is completed by 
a metal blade which may be caused to move into contact with the 
side of a metal jaw or between two metal jaws. A common form 
of single-pole blade switch is shown in Fig. 249. 

A snap switch is one in which the opening and closing of the 
electrical circuit, or circuits, which the switch is to control is 



Fig. 253 —Exploded view of drum switch used by 
Wagner Electric Co. 


performed by a snap action in the switch. This snap action is 
produced by a coil spring which winds up as the handle of the 
switch is turned. After a certain movement of the handle the 
spring is released and allowed to cause the contacting mechanism 
of the switch to rotate through a fractional part of a revolution. 
This rotation of the contacting mechanism is performed in a very 
short time, thus reducing the tendency for electric arcs to form at 
the points of make and break. An example of a snap switch is 
shown in Fig. 250, in which the switch cover is removed partially 
so that the interior is somewhat exposed to view. 

A plug switch is one in which the switching action is performed 
by moving a plunger in or out of an opening in the top of the 
switch cover. This plunger may be made of metal or insulating 






























326 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 254— Double-pole switch of the sliding type } in 
which there are two sets of contacts 

material, and if made of metal it may 
form part of the electrical circuit 
when the switch is closed, though not 
always. The plug itself may be so 
constructed that it can be removed and 
the switch made inoperative until the 
plug again is inserted. Plug switches 
usually are confined to the operation 
of ignition and lighting circuits. 

A rotating, or drum, switch, is one 
in which the switching operation is 
accomplished by a rotating member. 
Two good examples of switches of this 
kind are shown in Figs. 251 and 252. 
The switch shown in Fig. 252 is one 
used by the Leece-Neville Co. in the 
starting motor circuit shown diagram- 
matically in Fig. 249. The switch 
shown in Fig 252 is made by the Wag¬ 
ner Electric Mfg. Co. An exploded view of this switch is shown 
in Fig 253. 

The switching operation in the case of a sliding switch is accom¬ 
plished by moving a set of contacts so they complete a circuit be¬ 
tween fixed contacts. A double-pole switch of this kind is shown 
in Fig. 254, in which the figures 3 represent the movable contacts 



Fig. 255 —Example of 
thrust type of switch in 
which an end or thrust 
movement performs the 
operation 
































































SWITCHES AND PROTECTIVE DEVICES 327 

and the figures 2 represent the stationary contacts. The switch is 
in the open position as shown in the figure, and the movable con¬ 
tacts are controlled by the shifting rod 1. 

In certain types of switches, which might be called thrust 
switches, the switching operation is performed by an end or thrust 
movement of some part of the switch. A good example of a 
switch of this particular type is shown in Fig. 255, and its opera¬ 
tion is quite simple. The switch normally is held open by the 
coiled spring, but when sufficient pressure is brought to bear on 



Fig. 256 —Diagram of brush switch used in the 
Delco systems 


the button or pedal, the contacts may be brought into contact 
with each other and will remain in contact until the pressure on 
the pedal is removed. The action of the spring then will open 
the switch. 

A brush switch is one in which the switching operation is per¬ 
formed by raising and lowering one of the brushes on the ma¬ 
chine. A starting switch of this kind, as used on the Delco sys¬ 
tems, is shown in Fig 256. Depressing the starting pedal lowers 
the motor brush and at the same time makes the generator end 
of the machine inoperative by raising one of the generator 
brushes. 

A grounded switch is one in which no attempt is made to keep 
both terminals of the switch insulated from the frame of the car, 
and in fact one terminal is connected purposely to the switch 
housing or car frame. A switch of this kind is shown in Fig. 257. 

An insulated switch is one in which both terminals of the switch 







328 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

are insulated from the switch housing. A switch of this kind is 
shown in Fig. 258. 

Control and Location of Switches 

Switches may be classified conveniently according to the means 
employed in operating them into the following groups: 

Manually operated. 

Electrically operated. 

Combined manually and electrically operated. 

In the case of the manually-operated switch the opening or 
closing of the switch, or perhaps both operations, are performed 
by the movement of a lever, pressing a button, pulling or rotating 
a handle, etc., which is usually within easy reach of the driver of 
the car. The switch itself may be mounted directly with the con¬ 
trolling handle, button or knob, or it may be mounted in some 
more advantageous positions so far as the electrical circuit, of 



Fig. 257 —Grounded switch. One terminal 
is connected to the switch housing 


which it is a part, is concerned and the operating movement trans¬ 
mitted to it by suitable mechanical connections such as rods, 
chains and levers. It is especially desirable to locate the starting 
switch for the motor in such a position that the connecting leads 
to and from the switch will be as short as possible, and still have 
the switch within easy reach of the driver when he is in the 
driver *s seat. 

A manually-operated switch which is operated by a rod is 
shown in Fig. 249. The gear-shifting lever in this case is used 

















SWITCHES AND PROTECTIVE DEVICES 


329 


in imparting the necessary motion to the rod controlling the 
switch. An extra position is provided for the gear-shifting lever, 
and when in this position all the gears are out of mesh and the 
lever is connected to the rod R, which is connected by the second 
rod or link L to the lever of the switch. The rod R serves the 
double purpose of operating the switch and meshing the motor 
pinion G with the teeth on the edge of the flywheel. When the 
pressure is removed from the gear-shifting lever it will be re¬ 
stored to its neutral position, due to the action of the spring S. 
The motor-starting switch, shown in Fig. 259, is intended to be 
mounted directly under the floor board in front, or within easy 
reach of the driver, and the button is mounted on the upper end 
of a rod which extends through a hole in the floor board. 

In the case of an electrically-operated switch, the movements 
of the switch are controlled by electromagnets, which may be 
energized by closing a small switch within easy reach of the 
driver. This small switch completes the circuit from the storage 



“TERMINAL INSULATED 



Fig. 258 —Insulated switch. Both terminals 
are insulated from the switch housing 


battery through the winding of the electromagnet. The principle 
of a switch of this kind is shown in Fig. 260. Closing the push 
button switch completes the circuit from the grounded side of the 
battery, which in this case is the positive terminal, through the 
winding of the electromagnet in the starting switch and finally 
back to the negative terminal of the battery. 

In some cases the manual and electrical means of control are 
combined. A very good example of a switch of this kind is found 
on the Overland car. In this particular case the manual operation 













330 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of the starting switch cannot be performed unless a certain elec¬ 
trical operation has been performed previously, which serves 
to release the switch and permit the manual operation. 

Fuses and Circuit Breaker 

The primary object of a fuse is to provide a weak spot in an 
electrical circuit, which will be destroyed when the current the 
circuit is carrying exceeds its normal value and thus open the 
circuit, and perhaps prevent serious damage to valuable equip- 
ment. The ordinary link fuse consists of a piece of wire made 
from metal having a relatively low melting temperature. This 
piece of wire is connected in series with the circuit, usually by 
placing its two ends under the heads of two flat-headed screws. 




Fig. 259 —Starting switch to be mounted directly under the 
floor board in front 

These screws form the terminals of the gap in the electrical circuit 
in which the fuse is to be introduced. A typical fuse block for 
link fuses, as used by the Remy company, is shown in Fig. 261. 

In the inclosed type of fuse the fuse wire is incased in a glass 
or fiber tube, and this tube is provided with metal ends, as shown 
in Fig. 262. Special clips are provided for accommodating fuses 
of this kind, as in Fig. 263, which shows several of them mounted 
side by side. 

The circuit breaker is a protective device which serves to open 

















SWITCHES AND PROTECTIVE DEVICES 


331 


the electrical circuit in which it is connected without destroying 
any part of the device itself, thus not necessitating any replace- 



Fig. 260 —Diagrammatic drawing of electrically- 
operated switch 



Fig r 261 —Fuse block for link fuses as 
used by the Remy company 


ments. The operation of a 
circuit breaker, as used by 
the Delco company, may 
be explained by reference 
to Fig. 264. The circuit 
breaker winding produces 
a magnetic pull on an 
armature when carrying a 
current, which controls a 
set of contacts in the main 
circuit. If the current in 
the winding of the circuit 
breaker becomes excessive, 
due to any cause, such as 
a ground or short cir¬ 
cuit, the armature will be 
drawn toward the core of 
the electro-magnet and the 
contacts broken, which re¬ 
sults in the circuit being 
opened. As soon, however, 










































332 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

as the circuit is opened the magnetic action on the armature ceases 
and it returns to its original position, thus closing the circuit 
again. This cycle of operations is performed quite rapidly and 



Fig. 262 —Inclosed type of fuse uAre, incased in glass, left, 
and link fuse, right 




Fig. 263 —Special clips for accommodating Fig. 264 — Circuit 
inclosed type of fuse breaker as used by 

the Delco company 


results in a sound quite similar to that of an ordinary buzzer. 
Such a sound is an indication that something is wrong with the 
system, and an investigation should be made. 

















































CHAPTER XIX 

Electric Lamps 

Lamp Filaments 

T WO kinds of material are used in the construction of the fil¬ 
aments for motor car lights, tungsten and carbon, and these 
filaments are placed in two different kinds of bulbs or globes, 
one in which the exhausted air is not replaced, and the other in 
which the exhausted air is replaced with nitrogen gas. The first 



-e—e- 

Z 

Fig. 265 —Different forms of filaments of electric light 
bulbs 

kind of bulb is called the vacuum bulb, and the second is called a 
nitrogen bulb. 

Tungsten filaments should be used exclusively because of their 
greater efficiency, as compared with the carbon filament. The ex¬ 
treme tensile strength of the tungsten wire filaments, which is sev¬ 
eral times that of steel, enables these filaments to withstand with¬ 
out serious injury all the ordinary jar and vibration encountered 
in service. 





























334 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The filaments are formed into several quite different shapes, as 
shown in Fig. 265. The filament shown at A is not suitable for 
motor car lights, as it is not sufficiently well supported to withstand 
the extreme amount of vibration to which it would be subjected. 
The filament shown at B is called the loop back type and is used 
in lamps that have non-focusing reflectors, such as side and tail 



Fig. 267 —Typical headlights, side lights and tail light as 
made by Westinghousc 


lighta The loop is anchored in the middle, which tends to prevent 
vibration and hence breaking. The filaments shown at C and D are 
used where high candlepower is required and exact focusing of the 
lamp in the reflector is desired. The filament shown at E is just a 
straight piece of tungsten wire which is connected to two terminals 
mounted in the ends of a glass tube. Several complete lamps are 
shown at A, B and C in Fig. 266. 





ELECTRIC LAMPS 


335 


Classification of Lamps by Base 

There are four main types of bulb bases, omitting some special 
types such as those used by the Bosch company, for example. Two 
of these four main types are of the familiar screw type and are 
seldom used except in interior body work, while the other two, 
called the bayonet type, are in quite common use for all purposes. 
The Edison type base is often called the Ediswan and makes use 
of a spring-locking device that holds the bulb firmly in place 
against jarring and consequent loosening. The base for this type 
is cylindrical and carries two small projecting pins on the side 
and directly opposite each other. The socket into which the base 
fits is also cylindrical and of such dimensions as to make a rather 
loose fit. Two slots are cut along the sides of the socket, and when 
the bulb base is placed in position, the projecting pins slide into 
these slots. At the bottom the slots end in a small upturned notch 
so that the pins in the base will fit into the notches when the bulb 
is given a part of a turn. In the bottom of the socket are pins 
that press against the inner end of the base and keep the pins in 
place in the notches. 

One kind of bayonet base is provided with a single electrical 
contact in the center of the bottom of the base, this contact com¬ 
ing against a spring, or plunger, in the socket when the bulb is in 
place. The electrical circuit is completed through this contact on 
one side, while the other side is completed through the metal of 
the outside cylindrical portion of the base, where it comes in con¬ 
tact with the metal shell of the socket. This type of base is called 
the single-contact type and was designed primarily for use with 
the one-wire, or grounded, system of wiring, in which the shell 
of the socket is attached to the frame of the car and forms part 
of the electrical circuit through each lamp. A set of single-contact 
lamps is shown in Fig. 267. 

Another kind of bayonet base has two contact points on the bot¬ 
tom of the base, both being insulated from the metal shell and each 
other. The circuit is completed through these two contacts, and 
there are two springs, or plungers, in the socket that make con¬ 
nection with the contacts in the base when the lamp is in place. 
This is called the double-contact type of base and is used with the 
two-wire, or insulated return, method of wiring, in which both 
sides of the circuit are insulated from the frame or metal of the 


car. 


836 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

One form of the screw type of base is called the candelabra base, 
and the other one, which is of smaller form, is called the miniature 
base. Their construction is similar to those used on lamps for 
house lighting, except they are both smaller. A single contact 
carried in the center of the bottom of the base makes contact 
with a spring in the center of the bottom of the shell. The 
other side of the circuit is completed through the shell of the base 
and a thin shell inside the socket, threads being formed in these 
two parts so that the lamp will screw into the socket. 

The filaments of all the lamps are so designed as to length and 
diameter that they will take a practically definite current from a 
certain voltage source of electrical energy. If the lamps be oper¬ 
ated at a lower voltage than that for which they are designed, 
there will not be sufficient current sent through them to heat the 
filament to the required degree, and as a result the lamp will not 
burn up to its rated candlepower. On the other hand, if they be 
operated on a higher voltage circuit than they are designed for, 
ail excessive current will be sent through the filament, which will 
result in a lighter degree of heat than the lamp is expected to take 
care of, and as a result there will be a reduction in the useful 
life of the lamp, and if the voltage be sufficiently high the lamp 
may be burnt out almost instantly. The voltage ratings, of course, 
correspond to the voltages of the circuits on which the lamps are 
to be operated. The voltage of the circuits in motor car work 
usually is taken as a sixth more than twice the number of cells 
in the battery. Thus, a circuit connected to three cells would 
require 7-volt lamps, one connected to six cells would require 14- 
volt lamps, etc. 

The size of the filament depends upon the current the lamp is to 
carry, and the length of the filament depends upon the voltage the 
lamp is to work on. Thus, if the current rating of two lamps is the 
same, and they are designed for six and twelve cells, respectively, 
then the filament in the 12-volt lamp will be twice as long as the 
filament in the 6-volt lamp, etc. If the current ratings were in the 
same ratio as the voltage ratings, then the filament of the 12-volt 
lamp would be approximately twice the area and twice as long 
as the filament of the 6-volt lamp. 

The watts required for any lamp are equal to the product of its 
current in amperes and its voltage in volts. The tungsten filament 
lamps, depending on the candlepower, require from .95 to 1.25 


ELECTRIC LAMPS 


337 

watts per candlepower, while the carbon filament will require ap¬ 
proximately 2.5 watts per candlepower. The following is a list of 
the lights as used by one of the leading companies: 


Lights 

Headlights . 

Side lights. 

Tail light. 

Speedometer light (when used).. 

Meter light (when used). 

Dome light (when used). 

Pillar lights (when used). 

All the above are 7-volt lamps. 


Candlepower Amperes of Each 


15 

4 or 6 
2 
2 
2 

2 or 4 
4 


2.5 

.84 to 1.25 
.42 
.42 
.42 

.42 or .84 
.83 



Fig. 208— Lens-mirror type 
of reflector 


Fig. 269 —Method of clean¬ 
ing old reflector 


Lamp Reflectors 

In brief the object of a reflector is to provide a means of collect¬ 
ing the rays of light that emanate from the source of light in 
certain directions and re-direct them in such a manner that the 
light given out by the source of light is confined to a compara¬ 
tively small part of the space surrounding the source of light. 





















338 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The earlier forms of reflectors were in the majority of cases of 
such a shape that they did not intercept a very large portion of 
the light rays from the source of light and for this reason were 
quite inefficient. The construction of what is called the lens-mirror 
type of reflector is shown in Fig. 268. This shows a lamp which 
originally was constructed to use a gas burner but is now provided 
with a special electric light attachment which may be moved in 
or out of position as conditions may demand. In this particular 
case only the rays of light in a small zone back of the bulb are 
intercepted by the reflector and re-directed toward the front of the 
lamp. The reflectors shown in Fig. 271 are of what is called the 
parabolic type. The advantage of this type of reflector is that it 
intercepts a very large proportion of the rays of light and for this 
reason is much more efficient than the lens-mirror type. 

The proper selection of a reflector for a certain lamp depends 
almost entirely upon the use that is to be made of the lamp. Thus 
in side and tail lamps for example a much less efficient type of re¬ 
flector may be used than in head and spot lights. 

Care of Lamp Reflectors 

When the lamp reflectors become dirty or tarnished they may 
be cleaned and brightened, although the surface of the reflector 
will be somewhat damaged every time it is touched, no matter 
how carefully the work is done. Ordinary dust and small par¬ 
ticles of foreign matter may be removed by blowing it off, and 
if it does not yield to this treatment, a stream of clean cold water 
at a very low pressure may be directed against the surface of 
the reflector. When water is used the reflector should be allowed 
to dry and then wiped off carefully with a very soft piece of 
chamois skin. Alcohol may be, and if obtainable should always 
be, used in cleaning the silvered surface of a reflector. The alco¬ 
hol may be applied by means of a piece of clean soft chamois skin 
which has been moistened, the reflector being wiped over with 
a rotary motion starting at the bulb opening and gradually working 
cut toward the outer edge of the reflector as shown in Fig. 269. 
The chamois skin should be held against the reflector with a light, 
even pressure. 

After the reflector is tarnished quite a bit it may be polished 
by moistening the chamois with alcohol and then applying a small 


ELECTRIC LAMPS 


339 


quantity of jeweler’s rouge. After the tarnished surface has 
teen brightened, the polish may be put on by using a small quan¬ 
tity of the same kind of rouge on a piece of dry chamois skin. 
The rotary motion should be used in this case just as previously 
described. 

Focusing Lamps 

It is necessary that a lamp be in focus in order that the best 
results may be obtained from the lamp. There is a certain posi¬ 
tion in a parabolic reflector which corresponds to the focus point, 
and if a concentrated filament incandescent lamp be mounted in 



Fig. 270 —Direction of light rays for different positions of 
lamp in a parabolic reflector 

the lamp in such a manner that the source of light in the filament 
corresponds in position with the focus point of the reflector then 
the light thrown ahead of the lamp will be along the lines A, A, 
in Fig. 270. If the lamp is too far back in the reflector the light 
rays follow the lines B, B, and if the lamp is too far ahead in the 
reflector the light rays follow the lines C, C. In addition to the 
lamps being in proper focus their adjustment on the supporting 






340 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

brackets must be such that the light is thrown at the proper point 
on the road ahead. 

The bulbs may be adjusted by moving them back and forth in 
the reflector until the filament is in the proper relation to the 
curved surface of the reflector. Quite a number of lamps are 
made so that the bulb position may be changed by turning a small 
screwhead or nut mounted in the front or back of the lamp hous- 



Fig. 271—v Reflectors of the parabolic type. This type is more 
efficient than the lens-mirror type 

ing and exposed so that it is reasonably accessible. Two differ¬ 
ent types of adjustments are shown in Fig. 271. 

In focusing the headlights one lamp should be adjusted at a 
time. The bulb of one lamp should be removed or the lamp cov¬ 
ered up in order that the light from it will not interfere with the 
adjustment of the other one. The focusing, of course, should be 
done in a rather dark location in order that the best results may 
be obtained. When the adjustment is made on a road the lamp 
bulb should be moved back and forth until the light on the road 
is clean and as free from black spots as possible. If the lamp 
bulb is adjusted in a garage the light should be directed against a 
wall and the bulb moved until a clean and clear spot of light appears 
on the wall. 











ELECTRIC LAMPS 341 

After the lamps have been focused they should be moved on 
their brackets so that the spot of light will be directed to the 
proper point on the road and the desired distance ahead of the 
car. In some cases it may be necessary to bend the brackets in 
order to make the last mentioned adjustment. 

Wiring and Light Switches 

There are three general methods of wiring and connecting the 
lamps on a car, as follows: 

Single-wire system. 

Two-wire system. 

Three-wire system. 

These three different systems of wiring have been described 
in one of the previous chapters. 

The switches used in controlling the light very often are quite 
complicated in appearance and construction in order that the 
desired results may be accomplished. A front and rear view of 




Fig. 272 —Gray & Davis junction switch for controlling the 
lights in. a single-wire, or grounded, system 

a typical lighting switch is shown in Fig. 272. There are four 
different positions for the switch as shown in the front view. 

Dimming Headlights 

One of the simplest devices used in dimming the headlights 
consists of nothing more than a resistance which may be con- 


342 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 273 —Resistance connected in a series with lamps to dim 
headlights 




Fig. 274 —Lamps connected in series, above, for a dim light and 
in parallel, below, for full candlepower 












































































ELECTRIC LAMPS 


343 


candlepower than their rated value. The connections of a dimmer 
of this type are shown diagrammatically in Fig. 273. When the 
switch is on the point marked O the circuit is open; when it 
is on the point B the lamps burn at full voltage; and when it 
is on the point L the lamps burn at a voltage lower than their 
rated value. 

In some cases the lamps and switch are so connected that the 
lamps may be connected in series for a dim light and in parallel 
for full candlepower. A diagram of a system of this kind is shown 
in Fig. 274. 

The high candlepower electric lamps are the cause of a great 
deal of trouble due to the blinding glare they produce, and as a 



Fig. 27G —Double filament 


Fig. 275 —Double headlamp 


result the driver of a car is greatly annoyed when he is com¬ 
pelled to drive toward high-powered headlights. A great deal has 
teen done by various motor organizations and there has been some 
legislation to bring about a more reasonable use of high candle- 
power lamps. 

Two bulbs quite often are used in each headlight, as shown in 
Fig. 275. The second bulb is of low candlepower, and in addition 












344 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


it is out of focus. As it is inserted in the upper side of the re¬ 
flector, most of the light is directed downward, all of which results 
in practically no glare. A very similar result is obtained by 
the use of two filaments in a single bulb as shown in Fig. 276. 
The back filament is employed for the high candlepower light 
and is in focus while the outer filament is for the low candlepower 
light and is out of focus. 


■4 


CHAPTER XX 
Electrical Instruments 

T HE following electrical instruments are ones that commonly are 
encountered in motor car work, and their purpose and operation 
will be described in the following paragraphs: Ammeters, volt¬ 
meters, ampere-hour meters, wattmeters, and watthour meters. 

The ammeter is an instrument to indicate the value of the current 
of electricity in the circuit of which the ammeter itself is a part. 

The voltmeter is an instrument whose construction is such that 
it will give an indication of the value of the difference in electrical 
pressure between two points in an electrical circuit to which the 
terminals of the instrument are connected. 

An ampere-hour meter is an instrument for measuring the quan¬ 
tity of electricity passing through an electrical circuit in a given 
time, and its construction is such that it sums up the successive 
products of current and time and thus total quantity is registered 
on a dial by means of a pointer which moves over a graduated scale. 

The wattmeter is an instrument for measuring power, that is, 
current in amperes times electrical pressure in volts. Its construc¬ 
tion is a combination of an ammeter and a voltmeter, the product 
being indicated by a pointer which moves over a graduated scale. 

The watthour meter is an energy meter, and it sums up the 
products of the power and time and registers this product on a 
dial or dials located on the front of the instrument. 

Ammeters 

The operation of all ammeters depends upon some effect pro¬ 
duced by the electric current. They may be classified conveniently 
according to the particular effect of the current upon which their 
operation depends. The two most common effects of an electric 
current are its magnetic effect and its heating effect, and the 
majority of the ammeters on the market at the present time depend 
upon one or the other of these two effects for their operation, 
especially the magnetic effect. The chemical effect of a current 
may be used in measuring the value of the current, but this method 
is so little used in comparison to the magnetic and heating effects 


346 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

that the descriptions will be confined to the two most commonly- 
used effects. 

There is a magnetic field surrounding an electrical conductor 
in which there is a current of electricity, as explained in detail 
in one of the previous chapters, and the strength of the magnetic 
field varies with the value of the current in the conductor, increas¬ 
ing with an increase of current and decreasing with a decrease 
of current. The majority of the ammeters in use at the present 
time depends for their operation upon this magnetic effect of 
the current, and their chief difference lies in the method of apply¬ 
ing the effect to the operation of the different makes and models. 

Simple Form of Ammeter 

A very simple form of ammeter is shown diagrammatically in 
Fig. 277. M is a strong permanent magnet with its ends mounted 
inside the coil C through whose turns the current to be measured 
passes, connection to the coil C being made by means of the ter¬ 
minals T1 and T2. A small piece of soft wire, I, is mounted 
on a vertical shaft, P, which also carried a pointer, PI, with a 
balance weight, W. The balance weight provides a means of making 
the instrument read the same in any position. The magnetic 
action of the magnet M on the piece of soft wire is such that 
the piece is held in the position shown in the figure when there is 
no current in the coil, that is, it is held in a position corresponding 
to the direction of the magnetic field from the north to the south 
magnetic poles of the permanent magnet. 

The direction of the magnetic field due to the permanent mag¬ 
net is from left to right. If a current of electricity be sent through 
the coil C, a magnetic field will be produced around the coil, 
and the direction of the magnetic field inside or outside the coil 
may be determined by the following simple rule. When you look 
along a conductor in which there is a direct current, in the direc¬ 
tion of the current, the magnetic current surrounding this con¬ 
ductor due to the current in the conductor will be clockwise in 
direction. Let us assume that the direction of the current is 
toward the paper in the -wires shown in the left-hand cross sec¬ 
tion of the coil. With the current in the coil in this assumed 
direction, there will be a magnetic field about the left-hand cross 
section in a clockwise direction, or down through the center of 
the coil, and at the same time there will be a magnetic field about 


ELECTRICAL INSTRUMENTS 347 

the right-hand cross section in a counter-clockwise direction which 
also will be down through the center of the coil. This magnetic 
held which the current in the coil tends to produce cannot exist 
alone but combines with the magnetic field of the permanent magnet 
and forms a resultant magnetic field. These two magnetic fields 
may be thought of as two forces whose directions and values are 
shown diagrammatically in the small figure to the right. 

The line marked Em represents the magnetic field due to the 
magnet and its direction is toward the right as shown by the 
arrowhead. The line marked Fc represents the magnetic field 
due to the current and its direction is down and at right angles to 
Em. The lengths of the two lines represent the values of the 
fields to some convenient scale. The line R represents the re¬ 
sultant field, due to Fm and Fc, both in direction and in value 
to the same scale as Fm and Fc. The piece of iron, I, will move 
so that it is parallel to the direction of the resultant magnetic 
field, which results in the pointer PI being moved toward the 
right over the graduated scale at the top of the instrument. The 
amount of the deflection of the pointer PI from the zero position 
will depend upon the position of the resultant field R in relation 
to the field Fm, due to the magnet. The angle between R and Fm, 
of course, will depend upon the value of Fc, which in turn de¬ 
pends upon the size of the coil, the number of turns in the coil 
and the current in the coil. Now by properly adjusting the size 
of the coil and the number of turns, the value of Fc may be made 
such that when it is combined with Fm to form R, the angle be¬ 
tween Fm and R will be of the desired value. For example, the 
construction may be such that 5 amp. in the winding of the coil 
will produce a deflection, or movement, of the pointer PI from 
zero to the extreme right of the scale. 

If the number of turns in the coil be reduced to half, then twice 
the current in amperes will be required to give the same deflection of 
the pointer as originally was produced. The markings on the scale 
then would have to be changed to twice their present values. If the 
number of turns in the coil were increased to five times their pres¬ 
ent value, then only 1 amp. would be needed to make the pointer 
move from zero to the extreme end of the scale. 

The position of the pointer PI for various known currents in 
the coil may be marked, and after such a marking is made the 


348 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

instrument may be used for measuring electrical currents. The 
current the instrument can indicate will depend upon the turns in 
the coil C. This type of instrument sometimes is called the soft wire 
iron type. The direction of the deflection of the pointer from zero 
in an instrument of this kind will depend upon the direction of the 
current through the winding in the coil C, so that the current in C 
always must be in one particular direction if the pointer is to be 

deflected in a definite direction from the zero mark on the scale. 
Such an instrument can be used in measuring direct current only. 



Fig. 277 —Simple form of ammeter. This type can he used in 
measuring direct current only 

Plunger Type of Ammeter 

The instrument shown diagrammatically in Fig. 278 is known 
as the plunger type. It consists of a curved soft iron plunger, I, 
mounted on the end of an arm which is carried on the shaft P. 
A pointer, PI, and a balancing weight, W, also are mounted on 
the shaft P, and the whole system is held in a definite position by 
the coil spring S. When a current is sent through the coil C it 





















ELECTRICAL INSTRUMENTS 349 

magnetizes the soft iron core I, which then is attracted, or drawn, 
into the coil. The movement of the iron core will depend upon 
the number of turns in the coil C, the strength of the spring S 
and the current in the coil C. The spring and turns in C may be 
so adjusted that any desired current will produce a movement of 
the end of the pointer from one end of the scale to the other. 
Changing the turns in the coil will change the value of the cur¬ 
rent required for a complete movement of the pointer from one 
end of the scale to the other, and hence the current capacity of 



Fig. 278 —Plunger type of ammeter. This type can be used 
for either direct or indirect current 

the instrument is changed. The deflection of the pointer in an 
instrument of this kind is in the same direction regardless of the 
direction of the current, and such an instrument may be used in 
measuring an alternating or direct current. 

Magnetic Vane Ammeter 

The instrument shown in Fig. 279 consists of a coil of wire, C, 
wound on a hollow spool inside of which a piece of soft iron, 
Yl, called the vane, is mounted on a shaft, P, which is parallel 












350 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 
to the axis of the coil but does not correspond in position with 
the center of the coil as shown in the figure. A second piece of 

soft iron, Y2, is mounted on the inside edge of the opening of the 

coil and in about the same relation to VI as shown in the figure. 

The moving parts are balanced by the weight W, and the system 

is held in its zero position by the spring S when there is no cur¬ 
rent in the coil. When there is a current in the coil, the two pieces 
of wire are magnetized alike in polarity, both north poles at the 
upper end and both south poles at the lower end, or vice versa. 
The two pieces then will repel each other, which will cause the 
pointer to move over the scale. The field inside the coil is some- 



Fig. 279 —The magnetic vane type which 
measures both currents 


what stronger near the outer edge, and the piece of iron, VI, is 
acted upon by a force tending to draw it into this stronger field, 
which will be the result as the moving system rotates, due to the 
shaft P being off the center of the coil. These two forces on the 
piece of iron VI combine to produce a movement of the pointer 
which will vary in value with the current in the coil and the num¬ 
ber of turns. The direction of the deflection of the pointer from 
zero is independent of the direction of the current in the coil, 




ELECTRICAL INSTRUMENTS 351 

and the instrument may be used in measuring both direct and 
alternating currents. This kind of an instrument is known as 
the magnetic vane type. 

Most Widely Used Ammeter 

The instrument shown in Fig. 280 is the most widely used of 
the various instruments operating upon the magnetic effect of 
an electric current. It consists of a permanent magnet, M, pro¬ 
vided with two special pole pieces, P2 and P3, between which a 
cylindrical piece of soft iron, I, is mounted. A coil, C, is wound 



Fig. 280 —The most common type oj ammeter 

on a light aluminum frame and pivoted at the top and bottom so 
that it may rotate about the piece of iron I, the sides of the coil 
moving in the small gap between I and the pole pieces P2 and 
P3. The current is led into and out of the coil C by two spiral 
springs, one at the top and one at the bottom, which also serve 
to keep the coil in its zero position and to provide a restoring 
force against which the magnetic action of the current in the coil 
is to act. 












352 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

A pointer, or needle, is attached to the coil and moves over a 
suitable scale when there is a current in the coil. In instruments 
of this kind the wire used in winding the coil is very small and 
capable of carrying only a very small current. In measuring 
larger currents than the coil will carry safely use is made of what 
is called an ammeter shunt, which will be explained in one of the 
following sections. 

When a current of electricity is sent through the coil of the 
instrument shown in Fig. 280, a magnetic field is produced through 
the coil, and this magnetic field and the one due to the permanent 



Fig. 281 —Weston portable ammeter 

magnet tend to turn so that they are parallel to each other. Since 
the coil is free to turn, except for the action of the springs 
attached to it, there will be a movement of the coil, and the extent 
of this movement will depend upon the value of the current in 
the coil. The direction of the deflection of the coil will depend 
upon the direction of the current in the coil, and hence the instru¬ 
ment can be used only in measuring direct current. A Weston 
portable ammeter of this type is shown in Fig. 281. 

Hot Wire Ammeter 

When a current of electricity is produced in a wire there is a 
certain amount of electrical work done in causing the electricity to 
flow against the resistance offered by the wire, just as a certain 
amount of work is done in causing a current of water in a pipe or 
overcoming the resistance offered by the pipe to the free flow of 
the water. In each of the above cases the work done is converted 



ELECTRICAL INSTRUMENTS 358 

into heat. The amount of heat produced in the case of the water 
is in the great majority of cases quite small, and for this reason it 
is not given very serious consideration. The heat generated in the 
wire, when there is a current in the ware, depends on the resistance 
offered by the wire and also on the value of the current in the wire. 

A good example of the fact that there is heat generated in a 
wire in which there is a current of electricity is found in all the 

commercial electrical 
heating devices and in 
the incandescent lamp. 
The heat generated de¬ 
pends on the value of 
the current, and if it 
were possible to meas¬ 
ure the amount of heat 
generated in a given 
time, in a certain wire 
with a known value of 
current in the wire, it 
would be possible to use 
the same wire in meas¬ 
uring a current by ac¬ 
curately measuring the 
heat generated and from 
this computing the value 
of the current. This 
method of measuring a 
current is not commer¬ 
cially possible, and a 
more practical applica¬ 
tion of the heating ef¬ 
fect is used. 

The principal of an electrical instrument operating on the heat¬ 
ing effect of a current is shown diagrammatically in Fig. 282. A 
wire, AB, of comparatively high resistance, low temperature co¬ 
efficient and non-oxidizable metal, has one end attached to the 
plate C, then passed around a pulley, P, that is secured to a shaft 
8, and its free end is brought back and mechanically, though not 
electrically, attached to the plate C. The spring F keeps the wire 
under tension, it being attached to the plate C, which is so guided 



strument that operates on heating effect 
of current 


854 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

that it can move in a direction at right angles to the shaft S. An 
arm, G, also is attached to the shaft S, being counterweighted at 
the upper end by the weight W and split open, or bifurcated, at the 
lower end. A fine silk thread, T, lias one end attached to one of 
the arms at the lower end of G, then passed around a small pulley, 
II, which is mounted on a shaft that carries a pointer, I, and finally 
has its other end attached to the second arm of G. The material 
composing the arms of G is springy and serves to keep the silk fiber 
in tension. 

The current to be measured passes through the wire A, entering 
and leaving through two twisted conductors, as shown in the figure. 
When a current is passed through A it is heated and expanded, 
which usually results in the tension in A being less than that in B. 
The tensions originally were the same, and equilibrium can be re¬ 
stored only by the pulley P rotating in a clockwise direction. This 



Fig. 283 —Connections of ammeter shunt in parallel with coil of 

ammeter 


rotation of the pulley P causes the lower end of the arm G to move 
toward the left. The silk thread that passes around the pulley H 
causes it to rotate in a clockwise direction, and as a result the 
needle, or pointer, I, is deflected toward the right, being rigidly 
attached to the pulley. Changes in the temperature of the entire 
instrument affect both the wires A and B alike, and there is, as a 
result of this equal change in their lengths, no movement of the 
pointer I. An instrument of this kind always deflects in the same 
direction regardless of the direction of the current, as the heating 
effect of a current is independent of the direction of the current 




















ELECTRICAL INSTRUMENTS 


355 


through the part of the circuit being heated. An instrument of 
this kind may be used in measuring either direct or alternating 
current. 

Ammeter Shunts 

In certain types of ammeters, especially the D’Arsonval type, it 
is practically impossible to carry the total current to be measured 
through the coil of the instrument. To prevent the necessity of 
doing this, use is made of what is called an ammeter shunt. This 
shunt is nothing more or less than a low resistance, arranged to be 
connected in parallel with the coil of the instrument. In other 
words, the coil of the instrument and the shunt are in parallel and 
the total current divides inversely as the resistance of the two 
paths. This shunt may be connected permanently and inclosed in 
the instrument case or it may be outside the instrument proper and 
connected to the coil of the instrument by flexible leads. When 
the outside method of connecting the shunt and coil in parallel is 
used, shunts of different resistances may be used with the same 
coil and in this way the range of the current capacity of the instru¬ 
ment, increased. When shunts are used the reading of the ammeter 
scale will be correct for one particular shunt, but additional mark¬ 
ings must be provided, or the reading multiplied by a constant, 
for the other shunts. The current ranges for the different shunts 
are usually multiples of ten. 

The resistance of the coil in the different types of ammeters 
should always be as low as possible in order that the voltage re¬ 
quired to oVercome the resistance pf the ammeter be as low as pos¬ 
sible. The coil when in parallel with the shunt gives a lower total 
resistance than the coil alone. The proper connection of an am¬ 
meter with an inclosed shunt is shown at A in Fig. 283. The 
ammeter indicates the current taken by the motor M and the cur¬ 
rent in the voltmeter, which is very small and usually may be neg¬ 
lected without any appreciable error. 

Principle of the Voltmeter 

The voltmeter is an instrument for measuring the electrical pres¬ 
sure between two points to which the terminals of the voltmeter 
are connected. The fundamental principle upon which the volt¬ 
meter operates is exactly the same as that of the ammeter, the 
difference being in the resistance of the instrument. The deflec¬ 
tion of the pointer on an ammeter depends on the current through 



356 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the windings of the instrument, and this current will vary in value 
as the electrical pressure acting on the instrument varies in value, 
provided the resistance of the instrument is constant. Thus, if 
an electrical pressure of 1 volt produces sufficient current in the 
winding of the instrument to cause the pointer to move a certain 
distance over the scale, then 100 volts will cause the pointer to 
move the same distance if the resistance of the instrument is in¬ 
creased to 100 times its original value. If the resistance be in¬ 
creased to ten times its original value, then ten times the electrical 


Fig. 284 —Weston duplex instrument for electric motor cars, a 
combined ammeter and voltmeter 

pressure will be required to produce a certain deflection, etc. With 
a certain resistance in circuit, the deflection of the pointer will 
vary as the pressure between the terminals of the instrument, be¬ 
cause this variation in pressure causes the current through the 
instrument to vary in value. 

An instrument similar to the one shown in Fig. 278 may be 
changed from an ammeter to a voltmeter by changing the number 
of wires in the coil. Thus, if a current of 10 amp. is required to 
produce a certain deflection of the pointer when the instrument is 




ELECTRICAL INSTRUMENTS 


357 


used as an ammeter, the same deflection may be produced by 
sending a much smaller current through a larger number of wires 
when it is used as a voltmeter. The same thing is true of the 
instruments shown in Figs. 279 and 280. 

The proper connections of a voltmeter are shown at V in Fig. 
283. 

Combined Ammeters and Voltmeters 

Quite often an ammeter and a voltmeter are combined in a single 
instrument, which usually is spoken of as a duplex instrument. 
Such an instrument is shown in Fig. 284. In the duplex instru¬ 
ment the ammeter and the voltmeter, so far as their operation is 
concerned, are independent of each other. 

In some cases the same coil is used either as an ammeter or as 
a voltmeter. The internal connections of an instrument of this 
kind are shown diagrammatically in Fig. 285. The terminal 
marked plus, +, is used both for the ammeter and the voltmeter. 
When connections are made to the plus terminal and the terminal 
marked 30 A, the instrument will read a maximum current of 30 
amps. Changing from the 30 A terminal to the 3 A terminal, the 
maximum current will be 3 amp. When connections are made to 
the plus and 15 V terminals, a maximum pressure of 15 volts may 
be read, provided the key is depressed. 

In some cases a charge and discharge indicator is used instead of 
an ammeter. The operation of these devices is very similar to 
the instrument shown in Fig. 278, which usually is referred to as 
the soft iron instrument. When the current passes through the 
coil in one direction, the moving part is turned in one direction, 
and with a reversal of current the moving part is turned in the 
opposite direction. The words “ charge ’’ and 11 discharge ’’ ap¬ 
pear when the moving part is in its extreme position. An indi¬ 
cator of this kind is shown in Fig. 286. 

The Leece-Neville Co. manufactures an indicator which is a part 
of the cutout. A small target is attached to the armature of the 
cutout, and the position of the cutout is indicated by this target, 
which appears through an opening on the front of the case. The 
complete device is shown in Fig. 287. 

Ampere-hour Meter 

The ampere-hour meter is an instrument for measuring the quan¬ 
tity of electricity passing through an electrical circuit in a certain 


358 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

time. It usually consists of a rotating part connected to a system 
of gearing which operates one or more pointers that move over the 
dial on the front of the instrument. The construction and operation 
of the rotating portion is such that the rate at which it revolves 
varies directly as the current through the instrument. Thus if a 
current of 10 amperes causes the rotating part to make 1800 revolu¬ 
tions in one hour, then a current of 20 amperes will cause it to make 
3600 revolutions in one hour. Now 10 amperes for an hour is 10 
amp.-hrs. and 20 amperes for an hour is 20 amp.-hrs., etc. The gears 



the same coil is used as either instrument 
connecting the rotating part and the pointers and the markings on 
the dial should be such that each division on the dial corresponds to 
a definite number of ampere-hours. In some types of ampere-hour 
meters there is a difference in the rate at which the rotating por¬ 
tion revolves when the current through the instrument is reversed. 
This difference in the indication for the two directions of current 
may be varied, which permits the loss in a storage battery that is 
being charged and discharged through the ampere-hour meter to 
be taken care of. Thus the adjustment on charge may be such 
that the instrument reads 20 per cent slow and correct on dis- 


























ELECTRICAL INSTRUMENTS 


359 


charge. In such a case the battery input as shown on the dial of 
the ampere-hour meter would be the same as the battery output. 
A typical form of ampere-hour meter is shown in Fig. 288. 

Wattmeter 

The wattmeter is an instrument for measuring power, and briefly 
it is a combination of an ammeter and a voltmeter. One coil, or 
set of terminals, is connected in series in the circuit just as an 
ammeter is connected, and the other set of terminals is connected 
across the circuit just as a voltmeter is connected. The operation 
of the instrument is such that the deflection of the pointer is pro¬ 
portional to the product of the current in one coil and the electrical 



Fig. 28G —Battery indicator Fig. 287— Leece-Neville indicator 

pressure applied to the terminals of the other coil, which gives the 
power in watts. 

Watthour Meter 

The watthour meter is an instrument for measuring the total 
energy passing a given point in an electrical circuit. It consists 
of a rotating portion whose rate of rotation is proportional to the 
power in watts. The rotating portion causes one or more pointers 
to move over one or more dials by a system of gears. This system 
of gears and the markings on the dials are such that the pointers on 
the dials give a reading of the energy in watthours or kilowatt 
hours. The difference in the readings of the dials gives the energy 
consumption for the time intervening between the two readings. 





CHAPTER XXI 

Ignition Systems 

T HE ignition system of a modern motor car engine constitutes 
one of the most important elements of the engine and one 
which is absolutely necessary in order to insure engine operation. 
Its primary object is to afford a means of kindling or setting on 
fire the compressed mixture of gasoline, gas and air in the engine 
cylinder, and thus produce what is called an explosion. 



Early Methods of Ignition 

The early systems of ignition were quite different from those in 
use at the present time and a brief description of several of them 

will be given in the fol¬ 
lowing paragraphs. 

In the earliest forms 
of the gas engine, a 
flame burned near a 
valve in the head of the 
engine cylinder, and 
when the piston was in 
the proper position, the 
valve opened, thus per¬ 
mitting the flame to ig¬ 
nite the gas back of the 
engine piston. This 
method was used in the 
forms of engines in 
which the gas and air 
mixture was not com¬ 
pressed. 

It was later found de- 

sirable to compress the 
Fig. 288— Ampere-hour meter . . , , 

gas and air mixture be¬ 
fore exploding it and in such a case the open flame could not be 
used. A platinum tube was inserted in the side of the combustion 
chamber and this tube was heated to such an extent by means of a 
flame directed against its walls from the outside of the cylinder 




IGNITION SYSTEMS 301 

that the end inside the combustion chamber was maintained at a 
sufficiently high temperature to ignite the gas mixture. 

Later forms used the property of gases to fire or ignite them¬ 
selves if compressed to a sufficient degree, and others made use of 
the stored heat in the cylinder walls and head to fire the highly 
compressed charge. 

All of these various methods were not practical in their appli¬ 
cation to the gasoline engine as used on the modern motor car, due 
principally to the fact that they did not permit a flexible engine 
action which is essential in a good motor car engine. The elec¬ 
trical ignition systems are standard at the present time and the 
fundamental principles upon which they operate will be discussed 
in the following section. 

Low-Tension Ignition System 

A low-tension ignition system is one using an electric spark which 
is produced by a low voltage or pressure. In a system of this kind 
the spark is produced within the cylinder by breaking the electrical 
circuit between two pionts in the combustion chamber, called elec¬ 
trodes. The principle of this system is shown diagrammatically 
in Fig. 289. When the igniter contacts are closed in the combus¬ 
tion chamber of the cylinder, a current will be produced in the 
circuit by means of the storage battery. After the engine shaft 
revolves a small angle, the contact in the combustion chamber is 
broken and when this break takes place, there will be an electric 
arc produced between the two parts of the igniter. A coil of wire 
about an iron core is shown connected in series in the circuit. This 
coil has a strong magnetic field produced about it and through its 
center when a current is established in the winding. This magnetic 
field represents a certain amount of stored energy just as a wound-up 
clock spring, and when the circuit is broken, the energy stored in 
the magnetic field will take some other form. As the magnetic field 
surrounding the coil decreases in value, due to a decrease in the cur¬ 
rent in the coil, the lines of magnetic force which are supposed to 
constitute the magnetic field cut the various turns of wire forming 
the coil, and as a result there will be an electrical pressure produced 
in the winding of the coil. This pressure may be and usually is 
many times the value of the pressure produced by the battery and 
as a result it tends to maintain the arc between the two terminals 
of the igniter when the circuit is broken in the combustion chamber. 
The purpose of the coil then is to give a much hotter and longer 


36^ ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

spark than would otherwise be obtained. Sueh a coil, of course, has 
only one winding and they are usually called primary or low-tension 
coils. The application of an ignition system of this kind to a four- 
cylinder engine is shown diagrammatically in Fig. 290. In this case 
the source of electrical energy is either the magneto or the five dry 
cells, depending upon the position in which the ignition switch is 
thrown. 

The chief advantage of the low-tension ignition system is its free¬ 
dom from short-circuits caused by poor insulation of the electrical 



Fig. 289 —Principle of low-tension ignition 


circuit. This system of ignition, however, is of only historical in* 
terest so far as the motor car is concerned, as it has been discarded 
for several years and is now confined almost entirely to low-speed 
stationary engines. 

This system is commonly called the make-and-break system of 
ignition. 

High-Tension Ignition System 

The operation of the high-tension ignition system is based on the 
fact that when a sufficiently high electrical pressure is made to act 
upon an electric circuit in which there is a small gap, the electricity 































IGNITION SYSTEMS 


363 


will leap this gap and produce a small arc. The principal parts of 
a high-tension ignition system are shown diagrammatieally in Fig. 

291. B is a source of electrical energy such as a battery or low- 
tension magneto connected in series with the primary winding P of 
the ignition coil, the vibrator Y and the contactor C. The contact 
C is operated by the engine so that it makes contact at the exact 
time an ignition spark is required in the engine cylinder. 

When the contact C is closed, a current will be produced in the 
primary winding of the coil which magnetizes the iron core and the 
vibrator V is attracted to the core. When the blade Y moves away 
from the end of adjusting screw A the primary circuit is opened 
and the iron core is demagnetized and the vibrator returns to its 
original position, and this operation is again repeated in rapid suc¬ 
cession so long as the contact C remains closed. Each time the cur¬ 
rent in the primary circuit is established and destroyed, there is a 
high electrical pressure produced in the secondary winding. This 
high electrical pressure is of sufficient value to cause a current to be 
established between the terminals or electrodes of the spark plug, 
and thus produce the desired ignition spark. 

A four-cylinder combination is shown diagrammatieally in Fig. 

292. Two batteries are provided in this case and either one may be 
used by throwing the switch on either point 1 or point 2. 

Principle of Make-and-Break Spark Coil 

This system is sometimes called the jump-spark system. 

If a current of electricity be established in a wire there will be a 
magnetic field produced about the wire. The strength of the mag¬ 
netic field will depend upon the value of the current in the wire, and 
its direction will depend upon the direction of the current in th® 
wire. Any change in the value of the current in the wire will result 
in a change in the strength of the magnetic field, it increasing with 
an increase in the value of the current and decreasing with a decrease 
in the value of the current. A reversal in the direction of the cur¬ 
rent will result in a change in the direction of the magnetic field. 

Now if the wire be formed into a coil as shown in Fig. 293, a 
much stronger magnetic field will be produced inside the coil than 
was originally produced near the straight wire. Inserting an iron 
core inside the coil will increase the number of magnetic lines pass¬ 
ing through the coil due to the fact that iron is a better conductor 
of magnetism than air, just as copper is a better conductor of elec¬ 
tricity than iron. 

Let us now investigate what will happen when such a coil is con- 


304 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

neeted or suddenly disconnected from a source of electrical energ) 
such as a storage battery. Just at the instant that the circuit is 
closed, the current starts to increase in value at a very high rate, 
but it cannot reach its maximum constant value, which is equal to 
the electrical pressure divided by the resistance, in zero time for 
the following reason: As soon as there is any current at all in the 



wire there will be a magnetic field produced and this magnetic field 
will increase in strength as the current in the wire increases. While 
the magnetic field is increasing, the magnetic lines through the coil 
are increasing in number and an electrical pressure is set up in the 




















































IGNITION SYSTEMS 


365 


various turns of the coil whose direction in the circuit is just the 
reverse of the electrical pressure of the battery or other outside 
source of pressure producing the current. As a result of this pres¬ 
sure being produced in the circuit and since its direction is opposite 
to the direction of the current, the current will not build up in value 
as rapidly as it would if there were no pressure being produced. 
When such a circuit is opened there will be an electrical pressure 
produced, but its direction will be just the reverse of what it was 
when the circuit was closed or its direction will correspond to the 
direction of the current. Thus, this electrical pressure produced in 



a circuit due to any change in the value of the current in the circuit 
is always in such a direction as to tend to prevent any change taking 
place in the value of the current. An electrical circuit in which 
there is an electrical pressure produced when there is a change of 
current in the circuit is said to possess self-inductance. The value 














































366 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of the self-inductance of a coil will depend upon the number of turns 
in the coil, the size of the turns, the length of the coil and the kind 
of material forming the core. 

If an electrical circuit containing considerable self-inductance be 
quickly opened, there will be a tendency for the current to drop to 
zero value instantly, which would result in the magnetic field about 
the circuit being destroyed in a like time. This change in circuit 
and magnetic field does not take place instantly, because, as the 
magnetic field decreases in value there is a pressure produced which 
tends to maintain or prolong the current. The value of this pressure 
may be many times the value of the pressure of the source of energy 
and as a result it will be ample to maintain an electric arc between 
the two points where the circuit is being broken. The duration of 



this high pressure is determined by the time required for the mag¬ 
netic field to be reduced to zero value. 

The rapidity with which the current in a circuit containing in¬ 
ductance builds up in value when the circuit is closed and decreases 
in value when the circuit is opened depends upon the relation between 











































IGNITION SYSTEMS 


367 


the inductance of the circuit and the resistance of the circuit. The 
larger the resistance and the smaller the inductance, the less the 
time required for a certain change in the value of the current to 
take place. Thus the current in a certain circuit might build up in 
accordance with the curve, A, shown in Fig. 294, in which the height 
of the curve above the horizontal represents the value of the current, 
and the distance along the horizontal corresponds to time. If the 
resistance of the circuit be increased the current will rise in value 
more rapidly, but it will, however, not reach as high a maximum 
value. The operation of the coil may be such that the circuit is 
closed only for the time, T, as shown in figure and in such a case 



BUNDLE OF 
IRON WIRE 



Fig. 293 —Illustration of principle of makc-and-1)reak spark coil 

the value of the current in the circuit with the resistance in series 
will be greater than without the resistance. Hence it is sometimes 
possible to improve the operation of a coil by placing a resistance in 
series with it and thus increase the rapidity with which the current 
builds up. The effect of the resistance on the decay of the current is 
to cause the current to drop off in value more rapidly. 

The magnetic field surrounding the coil represents a certain 
amount of stored energy and it is this energy which is transformed 
into electrical energy when the circuit is broken, and then in turn 
converted into heat in the electric arc at the point of break. The 
greater the inductance of the coil and the larger the value of the 






















3(58 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

current the greater the amount of energy stored in the magnetic 
field. There is, however, a limit to the amount of energy required 
in the spark and it is not economy to design the coil so as greatly 
to exceed this value. 

Fundamental Principles of Jump-Spark Coil 

The construction of a typical jump-spark coil is shown in Fig. 295. 
It consists of two coils about an iron core. One of these coils, called 
the primary, is connected in series with a source of energy and a 
vibrator similar in principle to those used on an electric door bell. 



Fig. 294 —Curves showing the relation between current and time in 
an inductive circuit while current is increasing 


The second coil, called the secondary, is wound outside the primary 
and it consists of a relatively large number of turns as compared to 
the primary and of much smaller wire. 

Any variation in current in the primary winding will cause a 
change in the magnetic field within the secondary winding which 
will result in an electrical pressure being produced in the secondary 
winding while the change in magnetic field is taking place. In the 
operation of the coil, the circuit is controlled by a contact which in 


















IGNITION SYSTEMS 


309 

turn is opened and closed at a definite time in relation to the posi¬ 
tion of the piston in the cylinder of the engine. When this contact 
is closed, the current immediately builds up in the primary winding 
and of course magnetizes the soft-iron core. The iron core then 
attracts the iron armature or hammer, and it is drawn toward the 
core, which causes the electrical circuit to be opened at the contact 
on the end of contact screw T . As soon as the primary circuit is 
opened, the armature returns to its normal position, since there is 
not sufficient current to magnetize the iron core. Just as soon, 
however, as the electrical current is again closed at the end of the 
contact screw, assuming the other contacts are closed, the above op¬ 
eration will be repeated. Many cycles of this operation may be 



Fig. 295 —Construction of typical jump-spark coil 

completed during the time the contact in the primary which is con¬ 
trolled by the gas engine—the timer—is closed. 

While the magnetic field within the secondary winding, due to the 
primary current, is building up in value, there will be an electrical 
pressure produced in the secondary winding and its direction will 
be such as to produce a current which tends to oppose the change 
ir. the magnetic field. Likewise, when the magnetic field in the sec¬ 
ondary is decreasing in value, there will be an electrical pressure 
produced and its direction will be such as to produce a current which 





































370 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

tends to oppose any change in the magnetic field. It is thus seen 
that the building up and decaying of the current in the primary 
winding causes an alternating pressure to be produced in the sec¬ 
ondary winding. The value of this pressure in the secondary will 
depend upon how rapidly the magnetic field is changing and the num¬ 
ber of turns in the secondary winding. The change in the magnetic 
field depends upon the time constant of the primary winding, that 
is, the relation between the inductance and the resistance of the 
primary winding. The more rapidly this magnetic field can be 
changed in value, the greater the pressure induced in the secondary 
winding. 

Purpose of Condenser in Jump-Spark Coil 

The condenser used in combination with a jump-spark coil acts as 
an electrical shock absorber. It is connected across the breaker 



Fig. 296 —Hydraulic analogy of the condenser across breaker con¬ 
tacts 

contacts and when they open, the energy which would normally go 
into the arc is stored in the condenser, thus eliminating the serious 
troubles due to the arc. The current in the primary circuit is re¬ 
duced to zero more quickly and a higher voltage is produced in the 
secondary winding. 

The operation of the condenser might be compared to the opera¬ 
tion of a diaphragm, D, stretched across a tank or pipe connected 
around a valve, V, as shown in Fig. 296. If the valve be suddenly 
closed the diaphragm relieves the strain on the valve to a great ex¬ 
tent and thus allows the flow of liquid to be reduced to zero in a 
shorter time than it could be if no diaphragm were used. 



















CHAPTER XXII 

The Magneto 

E ARLY forms of ignition devices depended upon the primary cell 
entirely as a source of electrical energy, but it was found to be 
inadequate to meet the requirement imposed upon it by the motor 
car manufacturers, who demanded as reliable a source of energy 



magneto 

as it was possible to obtain. The use of the storage battery 
overcame some of the disadvantages of the primary cells, but 
the storage batteries had to be removed from the cars for 
charging. The storage battery, however, did not satisfac¬ 
torily meet the demands, and as a result the magneto was 
developed and applied to the motor car engine. Later, how- 











372 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


ever, suitable charging generators and regulating devices were de¬ 
veloped, by which the storage battery could be kept in a condition 
of charge without being removed from the car, and it is at present 
used as widely as any source of electrical energy for motor car 
engine ignition. 

Fundamental Principle of Magneto 

The fundamental principle upon which the magneto operates 
may be explained by reference to Fig. 297. A magnetic field is 
produced between the poles N and S of a strong permanent mag¬ 
net. A coil of wire C is mounted on a suitable shaft so that it 
may be revolved in the magnetic field of the magnet. Now, as 



Fig . 298 —Curve showing variation in value of electrical pressure 
produced in coil revolved in a uniform magnetic field 


the coil of wire revolves the magnetic lines of force which are 
supposed to form the magnetic field will be cut by the sides of the 
coil and as a result an electrical pressure will be produced in each 
of the two halves of each turn of the coil. The value of this pres¬ 
sure in any one of the wires at any instant will depend upon the 
rapidity With which the wire is moving across the magnetic lines 
in a direction perpendicular to them and also upon the strength 
of the magnetic field or the number of lines of magnetic force per 
square centimeter. An inspection of the figure will show that the 
two sides of each of the turns are moving parallel to the direction 






THE MAGNETO 


373 


of the magnetic field when the plane of the coil is vertical, and 
hence when the coil is in this position no electrical pressure will 
be produced in it. When the plane of the coil is parallel to the 
direction of the magnetic field the two sides of each turn are mov¬ 
ing perpendicular to the direction of the magnetic lines, and 
hence the lines of force are being cut at the greatest rate. It is 
interesting to note that the actual number of lines of magnetic 
force through the coil is at a maximum when the rate at which 
the sides of the coil are cutting the lines of force is at a mini¬ 
mum, and also that the actual number of lines of force through 
the coil is at a minimum of zero when the rate of cutting is at a 
maximum, or the sides of the coil are moving perpendicular to the 
direction of the magnetic field. 

For positions intermediate between those referred to in the 




Fig. 299 —Iron core for magneto 

preceding lines the value of the electrical pressure in the winding 
of the coil will depend upon the angular position of the coil with 
respect to a reference plane parallel or perpendicular 'to the 
magnetic field. The total pressure produced in the coil at any 
instant will be equal to the sum of the pressures produced in the 
several turns of the coil. The variation in value of this total 
pressure may be represented graphically by a curve, such as the 
one shown in Fig. 298. The distance along the horizontal cor¬ 
responds to the coils position in the magnetic field, and the distance 
of the curve above or below the horizontal line corresponds to the 
value of the electrical pressure in the coil. The direction of the 
olectrical pressure in the coil will change during the rotation of the 
coil as the movement of the two sides with respect to the magnetic 






374 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

field changes. This change takes place -when the electrical pres¬ 
sure in the coil is zero. The electrical pressure is said to be posi¬ 
tive for half a revolution and negative for half a revolution. It 
must be understood that these terms are only relative, and either 
part of the curve above or below may be considered the positive 
portion and the other part the negative portion, but it is common 
practice to think of the upper portion as being positive and the 
lower portion negative. 

An electrical pressure of this kind is called an alternating pres- 



Fig. 300 —Cross section of magnetic cir¬ 
cuit of magneto 


sure on account of its reversing in direction, and it would pro¬ 
duce an alternating current if it were to act on a closed elec¬ 
trical circuit. 

The time required to complete one cycle is called the period. 
Thus the period of a sixty-cycle current or pressure is V 60 sec. 














THE MAGNETO 375 

Each of the individual sets of positive and negative values is 
called an alternation. 

Simple Form of Magneto 

In the construction of the magneto the coil of wire is wound 
on an iron core similar in form to the one shown at A in Fig. 299. 
A cross-section through the iron core and coil is shown at B in 
the same figure. The iron core is mounted between pole pieces 
fastened to the poles of strong permanent magnets. Two cross- 



Fig. 301— Cross section of magnetic cir¬ 
cuit of magneto 


sections of the magnetic circuit are shown in Figs. 300 and 301 
respectively. With this construction the rate at which the mag¬ 
netic lines are cut is quite different from the case shown in Fig. 
297. The magnetic lines seem to be carried around with the iron 
core toward the trailing tips of the pole pieces, as shown in Fig. 





















376 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

300, and they then rather quickly change their direction through 
the coil around the core as shown in Fig. 301. The sudden change 
in the number of lines of force through the coil results in a high 
electrical pressure being produced in the winding of the coil. This 
high electrical pressure is as a rule quite desirable, as will be 
explained later. 


Four different positions of the iron core are shown in Fig. 302, 
and directly beneath them is shown a curve which represents the 
variation in the electrical pressure for all positions of the core. 



Fig. 302 —Variation in electrical pressure of magneto for different 
positions of armature core 


Operation of K. W. Magneto 

The operation of the magneto as explained in the previous 
section depended upon the rotation of a coil of wire in a mag¬ 
netic field, which resulted in the various turns of the coil cutting 
the magnetic lines of force forming the magnetic field, and this 
cutting of the magnetic lines resulted in an electrical pressure 
being produced in the coil. The same results could be obtained 
by allowing the coil to remain stationary and by some means in- 














THE MAGNETO 


377 


creasing and decreasing, and perhaps building up, the magnetic 
field through the coil in the opposite direction. In this second 
case there would be a relative movement of the turns of the wire 
forming the coil and the magnetic field, and this is the principle 
upon which the inductor type of magneto operates. 

The magnetic field is produced by strong permanent magnets, 
and a mass of iron is rotated between the poles of the magnets 
while the winding is stationary. A good example of a magneto 
of this kind is one manufactured by the K. W. Ignition Co. The 
moving element of the magneto is called the rotor, and it is shown 
assembled with the coil in position in Fig. 303. The winding is 
placed around the shaft and between two blocks of laminated 
(Iron. These blocks of iron are riveted to the shaft at right an- 



Fig. 303 —Rotor and winding of K. TP. 
magneto 


gles to each other. The pole pieces attached to the end of this 
permanent magneto are so shaped and placed in such a position 
that the magnetic lines in traveling across from one pole piece 
to the other find a path of low magnetic resistance, or reluctance, 
through the winding and one end of each of the masses of iron 
attached to the shaft. The value of the magnetic flux, or the num- 

































378 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ber of lines of magnetic force through the coil, will change as 
the reluctance of the path in which the magnetic lines travel 
changes, the flux increasing with a decrease in reluctance and de¬ 
creasing with an increase in reluctance. Each quarter turn of the 
rotor, or each 90 deg., the direction of the magnetic flux through 
the coil will be reversed; consequently, an electrical wave of pres¬ 
sure equivalent to one-half cycle will be produced for each quarter 
turn of the rotor. A cross-section through a K. W. high-tension 
inductor type magneto is shown in Fig. 304. 

Dixie Magneto 

The operation of the Dixie magneto in some respects is some¬ 
what similar to the inductor type, but in this case the pole pieces 
themselves revolve, and they do not reverse their polarity as in 
the case of the inductor type. The principle of the Dixie mag¬ 
neto may be understood easily by an inspection of Fig. 305. The 
pole pieces, as shown in the figure, are one-sided and mechanically 
connected by a non-magnetic section. Each pole piece will have 



Fig. 304— Cross-section of K. W. inductor 
type magneto 


the same polarity as the end of the permanent magnet immediately 
behind it. This arrangement results in two pieces of iron with 
opposite magnetic polarity revolving in a circle. A piece of iron 
in the shape of a letter V has its ends shaped to form an opening 
in which the pole pieces may revolve. A winding is placed about 
the bottom of this V-shaped piece of iron, Now, as the pole pieces 




























THE MAGNETO 


379 


are caused to revolve, the magnetic poles pass the ends of the 
V-shaped piece, which causes the magnetic flux produced by these 
pole pieces to reverse in direction through the winding. 

This magneto is unique in that magnets are placed the reverse 
way of the usual custom, at right angles instead of parallel to the 
rotative axis. 

The V-shaped piece is so arranged that it may be turned through 
a small angle relative to the permanent magnets. The object of 
this is to obtain the same intensity of spark for all positions of the 


spark. Thus when the breaker 
is rotated by the spark lever in 
advancing or retarding the 
spark, the coil and piece of 
iron on which it is wound is 
rotated at the same turn and 
exactly the same amount so 
that the same magnetic con¬ 
ditions are maintained. 

Berkshire Magneto 

The Berkshire magneto is a 
machine working on somewhat 
the same principle as the Dixie. 
Two cuts of this magneto are 
shown in Fig. 306. Referring 
to the figure, the two main 
poles of the magnets are A 
and B, while C and D are 
iron laminations running parallel to the armature as shown 
in the left-hand figure. The rotating armature is formed 
partly of iron and partly of aluminum. The iron parts are 
shown in black, and for the position of the armature shown 
in the figure the magnetic lines flow along the following path: 
From A to C through a portion of the armature, from C to D 
through the piece of laminated iron upon which the coil is wound, 
from D to B through another section of the armature and from B to 
A through the magnets. As the armature revolves and the iron 
parts come opposite the poles, instead of bridging the gap between 
them as sketched, there is no complete magnetic circuit through the 
core of the coil. This means that revolving the armature continually 
makes and breaks the magnetic circuit through the core of the coil. 



flux in Dixie magneto 











380 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


Simms Magneto 

A special feature of the magneto made by the Simms Magneto 
Co. is the design of the pole pieces, which have extensions on the 
edges following the direction of rotation of the armature. These 
extended edges keep the edges of the armature shuttle within the 



Fig. 306 —Berkshire magneto, which works on somewhat the 
same principle as the Dixie 


influence of the pole pieces for all positions from full retard to 
full advance. This results in the shuttle never being widely sepa¬ 
rated from the pole pieces when the current is broken. The shape 
of these pole pieces is shown in Fig. 307. 

Mea Magneto 

The magnets in the Mea magneto, instead of being of horseshoe 
form, are bell-shaped, as shown in Fig. 308. The entire magnet is 
carried in a trunnion mounting so that the field magnets may be 
turned to the same extent that the contact breaker is turned to 
give the necessary advance or retard of the spark, thus insuring 























THS MAGNETO 381 

that the circuit will be broken with the armature in the same rela¬ 
tive position with respect to the field poles. 

The method whereby this is accomplished is shown in Fig. 309. 
The relative position of the armature and field magnets are shown 
for both the full retarded and advanced positions of the spark. 
The movement of the magnets is against the direction of rotation 
of the armature when advancing the spark and in the direction 
of rotation of the armature when retarding the spark. 

Low-Tension Magneto 

The low-tension magneto, sb its name indicates, is one in which 
an electrical pressure of relatively low value is produced when 



Fig. 307 —Shape of pole pieces for Simms magneto 


the armature of the magneto is driven at ordinary, or working, 
speed. The winding of this type of magneto consists of a single 
coil of rather large wire, something like a No. 18 Baudsgage. 
The volume of current such a magneto is capable of supplying is, 
of course, greater than the current a high-tension type can supply, 
but this current is supplied at a relatively low voltage, so that the 
actual output of the two types of magnetos may be practically the 
same. The low-tension magneto is used with the make-and-break 
system of ignition its winding being connected directly in series 
with the ignitor points and, perhaps, an inductive coil, sometimes 
called a kick coil, which intensifies the spark. 

Since the electrical pressure generated in the winding of the 
low-tension magneto is so low, it is impossible to use such a mag¬ 
neto with jump-spark ignition systems without increasing the volt- 










382 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

age by an induction coil. Magnetos of the low-tension type then 
always are used with all induction coil, just as the battery is 
combined with the induction coil, when they are used in supply¬ 
ing current for jump-spark systems of ignition. 

The application of the low-tension magneto is shown diagram- 
matically in Fig. 310. A sectional view of a low-tension magneto 
is shown in Fig. 311. Each of the most important parts is given 
its proper name. 

The purpose of the high-tension distributor shown in Fig. 310 
and 311 is to distribute the high-tension current from the high- 
tension coil, shown at the right of Fig. 310, to various spark plugs 
when the interrupter breaks the primary circuit of the coil, which 
includes the winding of the magneto. The distributor brush should 



Fig. 308— Bell-shaped magnet 
Jor Mea magneto 


be making contact with or directly opposite one of the segemente 
connected to the spark plug wire terminals when the primary cir¬ 
cuit of the high-tension coil is broken. The distributor usually is 
mounted on the magneto and geared to the armature shaft in order 
that the position of the distributor arm and the cam, relative to 
each other in their respective cycles of operation, be practically the 
same, except for the advancing or retarding of the spark. 

As the cam on the end of the armature shaft shown in Fig. 311 ro¬ 
tates, it raises the interrupter, or breaker bar, twice each revolution, 
and this causes the primary circuit of the high-tension coil to be 
opened suddenly, which results in a high electrical pressure being 
induced in the secondary winding, provided the break in the primary 
circuit occurs when the armature is in such a position as to have a 
rather high electrical pressure induced in its winding, In a four-cyl- 














THE MAGNETO 


383 

inder, four-cycle engine, four sparks are required every two revolu¬ 
tions of the engine crank; hence, the distributor will be driven at half 
the speed of the engine crank. Since only two sparks are possible with 
this type of magneto for each revolution of the armature, it is neces¬ 
sary to drive the armature at twice the speed of the distributor, or at 
engine speed. In a six-cylinder engine, the distributor shaft revolves 
at half the engine speed, and the armature shaft at one and one-half 
engine speed in order that the required six sparks be produced for 
each two revolutions of the engine crank. 

the engine speed, and the armature shaft at one and one-half engine 



Fig. 309 —Relative position of armature and magnets 
for different postions of spark in Mea magneto 


speed in order that the required six sparks be produced for each two 
revolutions of the engine crank. 

High-Tension Magneto 

The high-tension magneto differs from the low-tension magneto 
in only a few particulars. The armature on the high-tension 
magneto is so wound that a high-tension current may be obtained 
from it without the use of a separate induction or high-tension 
coil. In some types, this high-tension current is produced in an 
armature winding of many more turns than is provided in the 
ordinary low-tension magneto, while in other types a second 
winding is placed around the first, which serves the same purpose 
as the secondary winding of the high-tension coil. This secondary 
winding is insulated carefully from the primary winding, except 
at one end, where both it and the primary winding are grounded. 
A cross-section of a typical high-tension magneto is shown in 
Fig. 312. PW is the primary winding, and SW is the secondary 
winding. The insulated end of the secondary winding is insulated 
carefully and connected to a metal collector ring, 0, mounted on 


384 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the armature shaft, and a small carbon brush, resting on this 
collector ring, takes off the secondary current and leads it to the 
distributor brush, Z. A cross-section perpendicular to the arma¬ 
ture shaft is shown in Fig. 313. A simplified diagram of the 
circuits of a high-tension magneto is shown in Fig. 314. The two 
metal points of the contact breaker normally are in contact. As 
the cam rotates one end of the bell crank comes into contact with 
an extension on the cam, which causes the bell crank to rotate, 
and, as a result, the two contacts are separated momentarily. 


DISTRIBUTOR 
GEAR 


(ARMATURE 

GEAR 


DRIVE 

GEAR... 



SPARK 

PLUG 


SEPARATE 
HIGH TENSION 
COIl 


Fig. 310 —Application of low-tension magneto, in which a 
high-tension distributor is used 


The primary circuit thus is opened and closed as many times for 
each revolution of the cam as there are projections on the cam. 

When the primary circuit is opened suddenly, an action will be 
taking place in the secondary winding, very similar to that taking 
place in the ordinary high-tension coil. At the same time there 
is a change in the magnetic lines of force through the secondary 
winding, due to a change in value of the number of magnetic 
lines, which, in turn, is due to the rotation of the armature in the 
magnetic field, which serves to increase the action taking place 
in the secondary winding. 

The purpose of the condenser, J, in Fig. 312 is to cause the 
current in the primary winding to decrease in value in a shorter 
time when the primary circuit is opened than it would otherwise, 
and at the same time to reduce greatly the amount of arcing at 
the breaker contact points. In some types of magnetos this con- 
































































































































































386 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 
denser is mounted inside the magneto armature, while in other 
types it is outside the armature. 

Safety Gap 

A device called a safety gap is provided on high-tension mag¬ 
netos, whose function is somewhat similar to a safety valve. 
If, for example, one of the high-tension leads from the distributor 
to the spark plugs should become detached so that the path through 
which the high-tension current ordinarily would flow would be 



Fig. 312 —Longitudinal cross-section through typical high- 
tension magneto, parallel to armature shaft 


open, then a very high voltage would be acting on the insulation 
and the insulation might be damaged seriously unless some easier 
path be provided for it to escape through. A magneto, of course, 
must be capable of generating a hot spark at slow engine speeds, 
and this results in a very high voltage spark being produced at high 
engine speds. 

The value of the electrical pressure produced in the secondary 

































































































THE MAGNETO 


387 

winding is limited by the distance between the spark plug points 
and the degree of compression in the engine cylinder. If these 
points are not in circuit, as previously explained, due to a broken 
or loose secondary wire, or if they are loose or apart, a very high 
voltage will be induced in the secondary winding. The possibility 
of such a destructive 
high-tension voltage be¬ 
ing generated in the 
secondary winding is 
prevented by connect¬ 
ing across the termin¬ 
als of the secondary 
winding an auxiliary 
gap, as shown in Figs. 

312 and 313. The gap 
between the two term¬ 
inals Z1 and Z2 is 
longer than the gap 
between the terminals 
of the spark plug and 
ordinarily no spark will 
pass between these 
terminals, but should 
one of the secondary 
circuits from the dis¬ 
tributor be opened ac¬ 
cidentally the electrical 
pressure in the second¬ 
ary winding will build 



Fig. 313— Gross-section of typical 
high-tension magneto perpendicular 
to the armature shaft 


up to a value just sufficient to jump the safety gap and no 
higher. 

Friction-Drive Magneto 


The very early forms of magnetos were driven by a small fric¬ 
tion wheel mounted on the end of the magneto shaft, and the 
magneto was so arranged and mounted that this wheel rested 
against the surface of some revolving portion of the engine, usu¬ 
ally the flywheel. In these cases it was not necessary that there 
be any definite relation between the speed of the engine and the 
sped of the magneto. The principal difficulty was the dangers re- 






























388 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


suiting from excessive speeds, and this was overcome by combin¬ 
ing a governor with the friction wheel in such a way that the 
driving action ceased when the speed of the magneto armature 
exceeded a predetermined maximum for which the governor had 
been adjusted. A magneto fitted with a friction drive and gov¬ 
ernor is shown in Fig. 315. A belt sometimes is used in driving a 
magneto but in no case where the speed of the magneto and engine 
must bear a definite relation to each other. 

Gear- and Chain-Drive Magnetos 

In all cases when it is necessary that the speed of the magneto 
armature bear a definite relation to the speed of the engine shaft, 
it is necessary to make use of either the chain or gear methods 
of driving. Gear drive is used more than the chain drive, and 



Fig. 314 —Simplified diagram of the circuits of a high-tension 
magneto 


the gears usually are made an integral part of the engine, or the 
same gears that are used in driving the pump or camshaft may be 
used in driving the magneto. Two typical methods of mounting 
and driving a magneto by gears are shown in Figs. 316 and 317. 
It is customary to mount the magneto on a bracket which is a 
part of the engine base or to provide a suitable mounting by bolt¬ 
ing a bracket to the engine base. Several methods of fastening 





































THE MAGNETO 


389 


the magneto in position are shown in Fig. 318. It always is bcot ' 
when possible to place the magneto on the inlet side of the engine 
and as far away from the exhaust pipe as possible, because the 
excess heat is likely to seriously injure the insulation. A flexible 
coupling usually is provided between the magneto and driving 
shaft to take care of any slight improper alignment of the two 
with respect to each other. 

When the magneto is driven by a chain, some means must be 
employed to keep the chain tight to keep the armature of the 
magneto and the engine shaft always in their proper relation. 

Impulse Starters 

The impulse starter is a special form of coupling which operates, 
in brief, as follows: The armature of the magneto is connected 



Fig. 315— Friction-drive magneto with governor 


to the driving shaft by a spring, and in starting the magneto arma¬ 
ture is prevented from rotating, which results in the connecting 
spring being compressed or wound up as the driving shaft rotates. 
After the driving shaft has revolved a certain angular distance, 
the armature of the magneto is released, and it jumps forward 
under the influence of the spring until it is caught again and the 


















390 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


cycle of operations repeated. During the rapid movement of th* 
armature, the magnetic lines of force will be cut at a high rate, 
which will result in a high electrical pressure being produced in 
the armature winding. By properly connecting the magneto gears 
to the engine, this high electrical pressure may be produced just 
at the instant that a spark is desired in one of the cylinders. 

The operation of a device of this kind as made by the Eisemann 
company may be explained by reference to the three cuts shown 
in Fig. 319. The coupling consists of two parts, a tube, A, which 
. is the driving member, and an inclosing cup, B, which is the driven 
member, the two being connected by a spring. There is a loose 
ring, C, within the cup, which is known as the trigger, and it has 
a lip which extends through a slot cut in the periphery of the cup. 
Mounted directly beneath the coupling is a notched bar, which is 
so placed that the notch is in line with the slot in the cup so that 
the trigger drops down under the action of gravity and holds the 
cup from rotating. This condition is shown in the ring, C, Fig. 
319. On the outside of the trigger ring there is a cam which en¬ 



gages a corresponding cam cut in the driving tube. After the lip 
on the trigger has become engaged with the notch in the notched 
bar, as shown in 0, the tube A continues to rotate and causes the 
spring, which is held between a driving pin, E, attached to the 
tube A and a block fixed to the cup B to be compressed. At a pre¬ 
determined point, the cam on the trigger ring engages the cam on 
the tube A and lifts the trigger high enough for the lip to 






































THE MAGNETO 


391 


disengage the notched bar, and the compression of the spring 
spins the cup around at a momentarily high speed in a clockwise 
direction. This momentary high speed gives a very hot spark and 
may be equivalent in intensity to one obtained under ordinary 
conditions at an engine speed of several hundred revolutions per 
minute. 

At slow speeds the cup is caught again and again as the driving 
member of the coupling causes it to rotate, but when the speed 
has attained a certain value, the trigger ring by its own weight 
becomes a ring governor and the centrifugal force keeps the lip 
from dropping through the slot in the tube B. A small lug on the 
inside of the trigger ring in line with the lip and on the same side 
engages a notch in the tube A and thus provides a positive drive 
so long as the speed is maintained. 

Sumpter Impulse Starter 

An impulse starter as made by the Sumpter Electrical Co. is 
shown in Fig. 320. It consists of a notched member, A, fast¬ 
ened to the end of the armature shaft, and a driving member, B, 



Fig. 317 —Magneto driven by extension of pump shaft 


which has two small extensions on its outer surface directly oppo¬ 
site each other. These two members are connected by springs as 
shown in Fig. 321, which also shows method of replacing springs. 
A small pin extends from the surface of the member B into the 
opening between the ends of the two springs. The short spring 



















































392 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

acts as a bumper spring and tends to absorb the shock of the 
longer spring when the armature the magneto is driven forward 





* Fig. 318 —Typical methods of holding magnetos in place 

suddenly. A pawl, C, is mounted in such a position that it will 
engage the notches in the outer surface of the driven member, A, 
os this member tends to rotate, provided the end of the pawl is 















































































THE M4GNET0 


393 


turned so that the action of the spring tends to press it down on 
the outer surface of the member A. Assuming the pawl is en¬ 
gaged in one of the notches in the member A and that the mem¬ 
ber B is rotating, then the long spring will be compressed. As the 
member B rotates, one of the extensions will move under the end 



Fig. 319 —Eisemann impulse starter, consisting of a notched 
member and a driving member 


of the pawl and raise it out of the notch in the member A and 
allow the member A to rotate momentarily at high speed until it 
automatically restores the pawl to the operating position when the 
speed drops below a certain value. 

The shape of the end of the pawl and the slots in the surface of 
the member A is such that the pawl is thrown out with such force 
when the speed has reached a certain value that it becomes en- 















































394 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


tirely inoperative as shown in the figure. It is then necessary 
to press the pawl down by hand. This type of impulse coupling 
however was found to have tw r o weak points. One was that the 
pawl would sometimes be thrown out while cranking the engine, 
and before it had started. The other fault was that when the engine 
slowed down to the point where the magneto spark was somewhat 
weak, the engine would miss. 

A later type coupling overcame these conditions by means of a 
member centrifugally operated. At medium and high speed the 
impulse feature of the coupling was rendered inoperative but at low 
speed the design was such that the impulse action was again 
obtained, so that no matter how slowly the engine might run, a hot 
spark was assured. 

Spark Timing 

The power output of a gasoline engine depends on the mean 
effective pressure developed in the engine cylinders. The value 



Fig. 320 —How the driving and notched members of 
the Sumpter are connected 


of the mean effective pressure is effected by three principal fac¬ 
tors : First, the compression to wdiich the gaseous mixture in the 
cylinders is compressed by the piston on its upward, or compres¬ 
sion, stroke just before firing; second, the exact time of the igni¬ 
tion spark in relation to the position of the piston, and third, the 
length of the stroke of the engine cylinder. It is readily seen that 
it is the second factor of the above three which concerns the prob¬ 
lem of ignition. To obtain the best results, the ignition of the 
gaseous mixture must take place at the time of maximum com- 


THE MAGNETO 


395 




pression, which corresponds 10 the uppermost position of the piston. 

Since there is both a mechanical and electrical lag in the re¬ 
sults obtained from the ignition spark, it is readily seen that 


Fig. 321 Eisemann device for advancing and retarding spark 
automatically 

the same setting of the spark which will give maximum efficiency 
at say 500 r.p.m. will be quite a bit too late for a speed of 1000 
r.p.m., and the spark would not then take place until the piston 


Fig. 322— Impulse starter 
made by the Sumpter Electri¬ 
cal Co. 

had started on its downward stroke and the pressure had dropped 
considerably, causing a very noticeable loss in power. Likewise, 
if an attempt be made to run the engine at a slow speed with the 





396 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


spark occurring at a time which gives the best results for high 
speed, there will be a marked loss in power, due to the fact that 
the explosion of the gaseous mixture takes place against th© rising 
piston. This condition of affairs Is indicated by a decided ham- 



Fig. 328 —Chart for determining relation hetiveen spark advance and 

piston travel 


mhVa 171 DEGREES 


































































THE MAGNETO 


397 


mering sound in the engine cylinders. In the majority of ignition 
systems means are provided for advancing and retarding the time 
of the spark in relation to the position of the piston. This change 
in spark position in the great majority of systems is accomplished 
by moving a lever, called the spark lever, which is within easy 
reach of the operator, while in some it is accomplished by an 
automatic device whose operation usually depends on the cen¬ 
trifugal action on one or more weights. In some cases the auto¬ 
matic and manual means are combined, and in a few no means of 
changing the position of the spark is provided at ali. 



Fig. 324 —Eiscmann high-tension magneto and automatic tim¬ 
ing device complete 


A centrifugal device for advancing and retarding the spark 
automatically as conditions may require is shown in Fig. 321. 

A convenient chart for determining the relation between the 
spark advanced in degrees for different piston strokes in inches 
with engines having strokes varying from 3 to 8 inches is shown 
in Fig. 328. The chart may be used as follows: Assuming the 
spark is to be advanced 30 degrees in an engine having a G-inch 
stroke, to find the amount the piston should travel trace the vertical 
line corresponding to the stroke in inches until it intersects the 
sloping line corresponding to the 30-degree line, and then follow 
the horizontal line to the left, which brings you out just a little 
below the J^-inch division. The piston then would have to travel 
a little more than inch below the uppermost position and moving 
upward in order that the spark have a 30-degree lead. 






CHAPTER XXIII 


Battery-Generator Ignition 

T HE fundamental principle of all battery ignition systems, to¬ 
gether with the main parts, is shown diagrammatically 
in Fig. 329. The electrical circuits for convenience may be spoken 
of as the low- and high-tension circuits, or the primary and secon- 



Fig. 329 —Diagram illustrating principle of all types of 'bat¬ 
tery ignition systems 


dary circuits respectively. The^ primary circuit consists of the 
following main parts, starting at the positive terminal of the 
storage battery and tracing along the circuit in the direction of 
the curves: The low T -tension, or primary, winding of the induction 































BATTERY-GENERATOR. IGNITION 399 

wil through the stationary and movable interrupter contacts and 
back to the negative or grounded terminal of the battery. The 
high-tension circuit consists of the following parts: Starting with 
the ground connection, you pass through the high-tension, or sec¬ 
ondary, winding of the induction coil to the center contact of the 
distributor head, through the distributor brush to the various con¬ 
tact points, depending upon the position of the distributor brush, 
to the spark plugs through the spark £ap and to ground. In some 
systems there is a small gap between the distributor brush and the 
various contact points, and it is necessary that this gap be bridged, 
in addition to the gap at the spark plugs, whenever a spar^; occurs 
in the engine cylinders. In the majority of systems, however, no 
such gap is provided, and the end of the distributor brush makes 
actual contact with the various points which are electrically con¬ 
nected to the spark plugs. 

Open- and Closed-Circuit Systems 

All battery ignition systems may be considered as belonging to 
either of two types of systems, called the open- and closed-circuit 
types respectively. The distinction between these two types may 
be understood readily by reference to the diagrammatic representa¬ 
tion of each as shown in Figs. 330 and 331. In the closed-circuit 
system the ignition cohtacts normally are closed and the operation 
of the cam opens these contacts. The contacts are shown in the 
open position in Fig. 330. In the open-circuit system the contact 
points normally are open and the operation of the cam closes these 
contacts directly or through the intermediate action of a system 
of weights or levers. The operation of the open-circuit system, as 
shown diagrammatically in Fig. 331, may be considered as taking 
place as follows: The spring is raised by the cam and suddenly 
lowered or released and its end strikes the end of the spring carry¬ 
ing the movable contact and thus causes the two contacts to be 
momentarily in contact with each other. In either system a high 
electrical pressure will be induced in the high-tension, or secon¬ 
dary, winding of the induction coil where the current in the pri¬ 
mary winding is interrupted, provided the primary circuit has 
been closed long enough to allow the primary current to build up 
in value so as to produce the necessary number of lines of mag¬ 
netic force through the secondary winding. 


400 ELECTRICAL EQUIPMENT OP THE MOTOR CAR 


Current Lag 

The current in the primary winding does not build up in value 
to its maximum value instantly, but an appreciable time is re¬ 
quired. The rapidity with which the current increases in value 
after the circuit is closed depends on the relation between the 
resistance and the inductance of the circuit. The higher the induct¬ 
ance and the less the resistance, the greater the time required for 
the current to reach a certain value, or, in other words, the slower 
the current builds up in value. 

Time Constant 

The value of the inductance of the circuit in henries divided by 
the resistance of the circuit in ohms gives the numerical value of 
what is called the time constant of the circuit, which is the time 
required for the current to rise to 63 of its maximum value. For 
example, if a circuit had a resistance of 2 ohms and an inductance 
of .0005 henry its time constant would be equal to .00025. If a 
pressure of 6 volts be impressed on this circuit the maximum cur¬ 
rent would be equal to six divided by two, or 3 amperes, and the 
current would reach a value of 1.89 amperes in .00025 second after 
the circuit was closed. 

The time constant of an ignition circuit, of course, can be 
changed in value, but it never can be equal to zero, as it is im¬ 
possible to reduce the inductance to zero. The intensity of the 
spark produced will vary its value as the value of the total num¬ 
ber of lines of force threading the secondary circuit and cutting 
the secondary winding when the primary circuit is broken varies 
in value. Hence, it is desirable to have the primary current reach 
as high a value as possible before breaking the primary circuit. 
In the closed-circuit system the primary circuit is opened a less 
number of times for low engine speeds than it is for high engine 
speeds, and the duration in time of each interval that the circuit 
is closed is greater. 

The relation between the time interval that the circuit is closed 
and the time interval that the circuit is open supposedly is the 
same regardless of the engine speed. Since the time intervals 
that the circuit actually is closed at any one time decreases as the 
speed of the engine increases, it readily is seen that the speed of 


BATTERY-GENERATOR IGNITION 


401 


the engine finally may reach such a value that the primary circuit 
may not be closed long enough to allow the primary current to rise 
to the necessary value to produce the required intensity of spark. 
As a result of this condition the current actually taken by the 
primary circuit of a closed-circuit battery ignition system, as indi¬ 
cated on a suitable ammeter, decreases in. value as the speed of 
the engine increases. The relation between current and engine 
speed for a four- and six-cylinder engine operated by a closed- 
circuit Atwater Kent ignition system is shown by the full lines 
in Fig. 332. 



Fig. 330 —Diagram of closed-circuit system of ignition, with con¬ 
tacts in open position 



Fig. 331 —Diagram of open-circuit system of ignition, with con¬ 
tacts in open position 


In the open-circuit type of ignition the primary circuit is closed 
for the same interval of time, regardless of the engine speed, and 
the primary current always builds up to the same actual value 
each time the circuit is closed. This results in the electrical pres¬ 
sure that is induced in the secondary winding and the spark being 
practically the same for all engine speeds. The current taken by 
such a system will increase in value as the speed of the engine 
increases. The relation between current and engine speed for a 
four- and six-cylinder engine operated by an open-circuit Atwater 
Kent ignition system is shown by the dotted lines in Fig. 332. 


















402 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The behavior of the various ignition devices may be investi¬ 
gated by a device called an .oscillograph and all well-equipped 
experimental laboratories are equipped with one. By means of 
the oscillograph the variation in primary and secondary current 
with respect to time readily may be investigated. The results 
of an investigation of both closed- and open-circuit types of igni¬ 
tion by the oscillograph are shown in Fig. 333. The two upper 
horizontal rows of curves are for an open-circuit type of system 
in which the primary circuit is closed for the same interval of time 
each time the circuit is closed. The upper row of curves indicates 



Fig. 332 —■Comparative current consumption for open- and 
closed-circuit ignition systems 


the same maximum value of secondary current, or voltage, for all 
engine speeds. 

The two lower horizontal rows of curves are for a closed-circuit 
type of system in which the primary circuit is closed for different 
intervals of times each time it is closed and the engine speed is 
different. For the high engine speeds the primary current is not 
closed long enough for the primary current to reach its maximum 
value, and hence the secondary current, or voltage, is not as high 
as it is at low engine speeds. 




































BATTERY-GENERATOR IGNITION 


403 


Atwater Kent Open Circuit System 

The operation of the open-circuit type of interrupter for the K3 
type of battery ignition system manufactured by the Atwater 
Kent Co. is in brief as follows: Four different positions of the 
interrupter in one of its cycles of operation are shown in Fig. 334. 
The ratchet A has as many notches as there are cylinders to be 
fired. The ratchet is mounted on the central vertical shaft of the 
device, which also carries a distributor and in this combined form 
is known as a unisparker. On four-cycle engines it is driven at 
half crankshaft speed, on two-cycle engines at crankshaft speed. 

The ratchet A engages the lifter B, and as A rotates its teeth 
or notches successively tend to draw B with them against the 
tension of the spring C. In doing so the head of B strikes the 


500 2 .P.M\ 

SECONDARY ^ 


1500 R.P.K 


2000 K.P.M. 35002.P.M. 

i 


PRIMARY 


. 5 
-jlooo 


SEC. 


ml two sec tmx| jofg-sEc | t i i i ^ sec 

L _ i -A -—/ -/l_—/ s\-i 

TYPE K-3 (open circuit) 


SECONDARY 


1 


\ _L 


A_ 


tmr|^- 0 SEc. 1 i 1 ‘- M i4q $ec 


=1)307 5EC - 


PRIMARY 


TYPE CC {closed circuit) 


Fig. 333 — Oscillograms, showing variation in primary and sec¬ 
ondary currents for ignition systems 


swinging lever, or hammer, D, whose motion in both directions is 
limited as shown, and the hammer communicates the blow to the 
contact spring E, bringing the contact points together momen¬ 
tarily. E is a compound spring, the straight member of which 
carries the movable contact, while the stationary contact F is 
mounted opposite it. The second member of this compound spring 
is curved at its end to engage the straight member. Ordinarily 
the straight spring blade is held under the tension of the curved 
blade and the contact points are held apart. When the curved 
blade is struck by the hammer D the points come into contact with 
each other. TJie curved blade, however, is thrown over farther by 

















404 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 334 —Diagrams showing operation of Atwater-Kent interrupter 

the impact and its hook leaves the straight blade. Upon reaching 
the limit of its movement, it flies back and strikes the end of the 













BATTERY-GENERATOR IGNITION 


405 


straight blade a blow, causing a very sharp break of the circuit. 
This movement is so extremely rapid that it cannot be detected by 
the unaided eye, so that its working cannot be tested simply by 
watching the operation of the contacts as in the case of a magneto 
interrupter. B, C and D of Fig. 334 show the successive move¬ 
ments of the parts during a single cycle. In A a notch of the 
ratchet has engaged B and is drawing it against the tension of the 
spring C. In the second sketch, B, the hook is just being released; 
m C the lifter is riding back over the rounded portion of the 


Fig. 335 —Location of condenser in Atwater-Kent open- 
circuit breaker 

ratchet and is striking the hammer D, which in turn pushes E for 
a brief instant against F. The return of B to the position shown 
in sketch D is so rapid that the eye cannot follow the movement 
of the parts D and E, which to all appearances remain stationary. 

Adjustment of the contact points is made by removing one of 
the three washers from under the head of the contact screw F, 
and the gap should be .010 to .012 inch, never exceeding the latter. 











400 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Where more accurate means of determining this distance are not 
available, it may be gaged with a piece of manila wrapping paper, 
which should be perfectly smooth. With the aid of a micrometer, 
a sheet of paper of the proper thickness can be selected. The 
contact points are of tungsten, and as the moving parts are all 
of glass-hard steel very accurately machined, the wear is negli¬ 
gible, so that adjustment is not required oftener than once in 

perhaps 10,000 miles 
and a replacement of 
contact points after 
running perhaps 50,000 
miles. 

In the latest models 
of this K3 type of igni¬ 
tion system, the con¬ 
denser is located with¬ 
in the timer-distribu¬ 
tor unit and in very 
close proximity to the 
contacts. The location 
of the condenser is 
shown in Fig. 335, and 
the complete timer-dis¬ 
tributer unit is shown 
in Fig. 336. This ar¬ 
rangement permits a 
reduction in the size of 
the condenser and at 
the same time increases 
its effectiveness. An 
automatic spark-ad¬ 
vance mechanism is 
provided, which oper¬ 
ates by centrifugal force, and this automatically advances the 
time at which the circuit is made and broken to compensate for 
the increase in speed. 

Atwater Kent Closed-Circuit System 

The Atwater Kent closed-circuit battery ignition system is 
styled model CC. It is quite different from anything else of 



Fig. 336 —Complete Atwater-Kent timer- 
distributor unit for K 3 systems 


BATTERY-GENERATOR IGNITION 


407 


its kind and is marked by great simplicity,. light weight of parts, 
very few moving parts, an absence of any bearings in the contact¬ 
carrying arm and compactness. 

The base on which the unit is built up is an iron casting 
on which the various parts are screwed rigidly. The whole device, 
consisting of timer, distributor and coil and mounted on a magneto 
type of base, is shown in Fig. 337. The breaker is shown in Fig. 
338. The contact arm is an exceptionally light steel stamping 
tipped with fiber where it touches the cam. The arm is riveted 



Fig. 337 —Atwater Kent model CG battery ignition system 
mounted on magneto base 


to a short length of spring steel, D, which in turn is riveted to 
the block L. The distributer cover is Bakelite, with the terminals 
molded in place. There is no wiping contact in the distributor, 
the air gap between the nickel alloy distributor blade and the 
terminals being .015 to .020 inch. The specially shaped cam has 
been adopted only after long experimentation, during the course 








408 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of which it developed that even the slightest variation in the 
radius of the curved portions between the flats exerted a power¬ 
ful influence on the character of the spark. 

Rotation of cam brings its corners in contact with the fiber tip 
T of the contact arm A, thus separating the contacts and break¬ 
ing the circuit. The contacts are together for a considerable 
period, thus permitting the coil to be saturated thoroughly. 

The contacts are of tungsten, the one in the arm being forced in 
place. There is but a single adjustment. To alter the size of the 
gap between the contacts the screw S is loosened and the arm B 
moved the required distance. The light weight of the contact 



Fig. 338 —Model CG Atwater Kent breaker, the drawing show¬ 
ing the operation of breaker 


arm is an important factor in the operation of the breaker. In 
addition to reducing -wear to a minimum, it eliminates harmonic 
vibration and operates to intensify the spark at high speeds. 

The condenser is located as close to the contact as possible 
to increase its efficiency. On account of its proximity to the 
contacts, this condenser needs to be only about a sixth the size 
that would be required were it located in the coil container as 
commonly done. Furthermore, the condenser is much more acces¬ 
sible in this location, though it is rarely necessary to touch it at all. 

The current consumption of this system is comparatively low at 
low speeds and does not fall off as fast at high speeds as might be 

















BATTERY-GENERATOR IGNITION 


409 


expected. Throughout the entire range the consumption is suf¬ 
ficient to insure a hot spark. 

Bosch System 

The Bosch battery ignition system consists of a combination 
breaker and distributor and a combined switch and coil, the 
latter being mounted on the dash so that the switch is within 
easy reach of the driver. The complete system is shown in Fig. 



Fig. 339 —Complete Bosch battery ignition system, including com¬ 
bination breaker and distributor and combined switch and coil 


339. The breaker mechanism is shown in Fig. 340. Rotation of 
the cam C causes the arm carrying the movable contact to move 
in such a manner as to open the circuit. The contacts are held 
closed by a spring, except when the projections on the cam are 
under the fiber block attached to the arm. 

The distributer mechanism is mounted directly over the breaker 
and is quite simple. It consists of the customary cover, with the 
terminals molded in place. A radial arm carries a carbon brush, 
which makes a wiping contact with the various terminals for 




















410 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the wires leading to the different spark plugs. A cross-section of 
the combined breaker and distributer is shown in Fig. 341, and 


an exterior view is shown in Fig. 



Fig. 340 —Breaker mechan¬ 
ism of Bosch system 



Fig. 341— Cross-section of 
Bosch combined breaker 
and distributor 


342. 

The switch is so arranged that 
a magneto may be used, and the 
engine will run on the magneto 
with the switch in, one position 
and on the battery with the 
switch in the other position. A 
vibrator attachment is incorpor¬ 
ated with the switch to facili¬ 
tate starting the engine when it 
is cold or the carbureter is out 
of adjustment. This vibrator 
mechanism is controlled by a 
pointed button in the center of 
the switch plug. Under normal 
starting conditions momentary 
pressure on the button will pro¬ 
duce a single spark at the plug 



Fig. 342— Exterior view of 
Bosch combined breaker and 
distributor 









































BATTERY-GENERATOR IGNITION 


411 


if the distributer brush is making contact with one of the dis¬ 
tributer terminals. Turning the button to the right and depress¬ 
ing it makes the necessary connection to provide a stream of 
sparks at the different 
plugs, depending on 
the position of the dis¬ 
tributor arm. If de¬ 
sired, the button can 
be locked in this posi¬ 
tion until the motor 
has started. 

There is only one ad¬ 
justment, and this is 
for the gap at the con¬ 
tacts. With the fiber ~ 

Fig. 344 —Breaker mechanism of Con- 

block attached to the necticut ignition system 




Fig. 343 —Complete Connecticut battery ignition system, which 
operates on the closed-circuit principle 


movable arm resting on the top of one of the projections on the 
cam, the contacts should be separated about .01 inch. To alter 
the adjustment the lock nut holding the stationary contact must 
be released first, and then carefully secured after the adjustment 
is made. 
























412 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Connecticut System 

The Connecticut system operates on the closed-circuit princi¬ 
ple and is made for four-, six- and eight-cylinder engines. The 
complete system is shown in Fig. 343. The breaker mechanism 
is shown in Fig. 344. As the cam C rotates the high parts come 
into contact with the roller R in the arm A, and thus separates 
the contacts. The arm A is returned to its normal position by 
a spring. The breaker mechanism is mounted on a plate which 
rests in the casing and is held in place by a spring ring and 
solid ring, the latter being held by two screws. The advance 


lever engages a stud on the breaker plate, the whole plate being 
advanced around the shaft to advance the time of ignition. The 
various parts of the combined breaker and distributor are shown 
in Fig. 345. The complete device with the distributor cap re¬ 
moved is shown in Fig. 346, and complete with the cap in posi¬ 
tion in Fig. 347. The operation of the advance lever in bringing 
about a proper timing is shown in Fig. 348. 

A very ingenious device is provided to prevent the possibility 
of the battery being exhausted, due to the ignition switch being 
left closed and the engine stopped. This device is a small 


Fig. 345 —Various parts of combined breaker and distributor 
of Connecticut system 



BATTERY-GENERATOR IGNITION 113 

thermostat connected in series with the primary circuit, which 
controls a mechanism similar to that in an ordinary door bell. 
If the engine happens to be stopped with the ignition switch 
closed, the primary current in passing through the thermostat 
heats it, thereby bending it and closing a circuit through a buzzer 
mechanism. This in turn automatically opens the switch. The 
action of the thermostat can be set for anything from 30 sec¬ 
onds to 4 minutes, the normal setting being about three-quarters 
of a minute. 

In the latest designs a spark gap has been provided between 


Fig. 346 —Connecticut com¬ 
bined breaker and distrib¬ 
utor with cap removed, 
above, and complete, right. 
Fig. 347 


the distributor brush and the contacts instead of a wiping con¬ 
tact. To prevent oxidization the cover is ventilated through two 
tiny holes so as not to decrease the weatherproof properties of 
the instrument. Rotation of the distributor arm acts to keep 
the housing well ventilated. The wiring to the coil is so ar¬ 
ranged through the use of a hexagonal terminal that it is im¬ 
possible to put a wire on the wrong connection. 


Pittsfield System 

The Pittsfield system operates on the open-circuit principle and 
is entirely different from any of the other open-circuit sys- 



414 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


terns. The principal point of difference is that contacts are 

brought together mechanically and separated mechanically, 
neither operation depending on the operation of a spring. The 
breaker, distributor and coil all are a single unit and the systems 
are supplied for four-, six-, eight- and twelve-cylinder engines. 
The inter-relation of the different parts is shown in Fig. 349. 
The breaker mechanism is shown in Fig. 350. 




Normally the contacts are separated. Rotation of the cam C 
presses the arm carrying the lower 
contact up, thus bringing the con¬ 
tacts together mechanically with a 
firm pressure and so holding them. 

Further rotation of the cam brings 
it in contact with the fiber member 
F on the end of the arm carrying 
the second contact, thus positively 
breaking the circuit. Still further 
rotation of the cam relieves both 
arms, and the contacts remain sep¬ 
arated until again brought together 


Fig. 348 —Operation of spark ad- Fig. 351 —Pittsfield battery ig- 
vance lever on Connecticut nition system complete 


by the rotation of the cam. The only , adjustment is that which 
has to do with the opening of the contacts, and these are easily 
accessible from outside the casing. Removal of the distributor 
cover and coil exposes the distributor mechanism, and after the 
key holding the camshaft has been withdrawn the whole shaft 








BATTERY-GENERATOR IGNITION 


415 


can be lifted out in case this should be necessary. The complete 
device is shown in Fig. 351. 

Remy System 

The Remy system operates on the closed-circuit principle, 
and it is distinguished by the fact that it has but two moving 
parts the cam and the breaker arm. The complete system is 










1 



Figs. 349 and 350 —Interrelation of parts in Pittsfield system, left, 
and breaker mechanism of Pittsfield 


shown in Fig. 352. The breaker mechanism is shown in Fig. 353. 
The rotation of the cam C brings its corners in contact with a fiber 
rdug which is riveted to the breaker arm. The arm thus is lifted, 
separating the contacts. Only hand advance of the breaker mech¬ 
anism is provided. 























416 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Another particular feature of the Remy unit is that the whole 
mechanism is stationary. Advancing or retarding the spark does 
not move any of the wiring. This is accomplished by mounting 
the breaker mechanism on a plate. This plate is attached to the 
advance lever and is moved with it, thus rotating the breaker 
mechanism partly around the cam. 

The distributor mechanism consists of the usual Bakelite cover, 
with terminals molded in place. There are no wiping contacts, 
the spark jumping from the radial distributor arm to the terminals 
and thus eliminating wear. 



Fig. 352 —Complete Remy battery ignition system, which operates 
on the closed-circuit principle 

A small resistance coil is located on top of the ignition coil and 
is connected in series with the primary winding. The object of 
this resistance is to protect the winding and at the same time 
prevent an excessive drain on the battery should the engine be 
left idle for any length of time with the ignition switch closed. 
The protection is provided by the resistance of the coil increasing 






















BATTERY-GENERATOR IGNITION 


417 


very rapidly when the current through it exceeds a certain value 
or, what amounts to the same thing, when its temperature exceeds 
a certain value, thus causing the resistance to increase very 
rapidly. 

The makers claim that the contact points, which are iridium- 
platinum, or tungsten, should not require attention more than 


twice a season. These contacts 
flat file so that surfaces will be 



Figs. 353 and 354 — 
Breaker mechanism of 
Remy, abovej and com¬ 
bined breaker and dis¬ 
tributor of Remy bat¬ 
tery ignition system 


should be dressed with a fine 
smooth and parallel, and they 



should be adjusted with the wrench provided by the makers so 
that the maximum opening is from .020 to .025 inch or the thick¬ 
ness of the gage piece riveted to the wrench. 

If the engine misses when running idle or at light loads the 
gaps at the plugs should be wider. If the engine misses when 
running at high speeds or when pulling hard the gaps should be 
narrower. 

The oiler on the shaft should be kept filled with medium cup 


















418 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Rhoades battery igni¬ 
tion system, which is 
compact and simple 


grease and screwed down two 
or three turns occasionally. On 
some of the devices a wick 
oiler is used, and in such cases 
pure vaseline should be used 
instead of the cup grease. The 
complete combined breaker 
and distributor of the Remy 
company is shown in Fig. 354. 

Rhoades System 

The Rhoades system op¬ 
erates on the open-circuit prin¬ 
ciple, and in its new form it 
has been amplified consider¬ 
ably, though the principle re¬ 
mains unaltered. The couple 
system is shown in Fig. 355 
and consists of the combined 
breaker and distributor unit 
and a combined coil and switch 
unit. 



Fig. 356 —Breaker mechanism 
of Rhoades system 


The breaker portion of the breaker-distributor unit is shown 
as seen from the top, in Fig. 356. The cam C is mounted loosely 
on the shaft and rotates with it by contact with the pin P, which 
is rigid, so far as rotation is concerned, with respect to the shaft. 
As the cam C rotates it presses the arm A outward, and this arm 

























BATTERY-GENERATOR IGNITION 


419 


in plunging back, hits against the lever L, thus forcing the con¬ 
tact together momentarily. 

If the cam is rotated in the reverse direction it simply rides 
over the pin and does not bring the contact together. The con¬ 
tacts, it must be remembered, are brought into contact solely by 
the momentum of the arm A, and for this reason the duration of 
contact remains the same regardless of engine speed. The charac- 



Fig. 357 —Complete Westinghouse tattery ignition system 

teristics of the spark then should be the same for all engine speeds. 

The distributor is the usual Bakelite construction with brass ter¬ 
minals molded in place. The distributor arm is keyed to the shaft 
■with a set screw, and the construction is such that it cannot b? 
assembled improperly. The distributor arm does not make con¬ 
tact with the terminals, but the spark jumps a small air gap. 

There is only one adjustment to make on the device and that 
is to regulate the distance between the contacts. They shoujd 































420 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

be about & in. apart at all times. Since the action of the device 
is entirely too rapid to be seen, care must be taken that each of 
the parts is functioning properly. 

There is a single oil cup on the distributor and this should re¬ 
ceive a drop of light machine oil twice a week for continuous 
driving. From time to time the cover should be removed, and if 
the cam appears dry, a very small quantity of thin oil may be put 
on it. Under no circumstances should the tension of the various 
springs be altered at all. 


Westinghouse 

The battery ignition system manufactured by the Westinghouse 
Electric & Mfg. Co. operates on the closed-circuit principle. The 

complete system, breaker, 
distributor and coil, is 
self-contained as shown in 
Fig. 357. The unit oper¬ 
ates in a vertical position, 
and its shaft is driven 
from the cam, or magneto, 
shaft through suitable 
gearing. The case of the 
instrument measures ap¬ 
proximately 3% inches in 
diameter and 5 inches in 
height. 

The breaker mechanism 
is shown in Fig. 358. It is mounted beneath the coil, while the dis¬ 
tributor mechanism is directly above the coil. Since, the system 
operates on the closed-circuit principle the contacts normally are 
closed. In operation, rotation of the cam separates the contacts 
against the action of a small spring under the left-hand side of the 
arm, A, as shown in Fig. 358. This spring always is under com¬ 
pression. The cam is mounted loosely on the shaft, but a small pin 
in a collar, or hub, on the shaft against which the cam rests enters 
a hole in the cam and provides the necessary driving connection. 
The breaker mechanism operates equally well in either direction, 
and a backward travel of approximately 48 deg. is possible without 
mousing the contacts to separate, which might result in a disastrous 
uack-fire of the engine. 



Fig. 358 —Westinghouse breaker 
mechanism 






BATTERY-GENERATOR IGNITION 


421 


The condenser is mounted close to the breaker mechanism in a 
special compartment cast integral with the main base plate. This 
compartment is on the same level as the breaker mechanism, but 
on the opposite side of the shaft, as shown in Fig. 358. The con¬ 
denser, coil and breaker are inclosed in a tube of Bakelite Micarta, 
which forms the body of the unit. Several openings are cut in 
the lower end of this tube to provide a means of making the neces¬ 
sary internal electrical con¬ 
nections and to give access to 
the breaker mechanism for 
inspection, cleaning and ad¬ 
justment. A short thin tube 
is placed over the main tube, 
forming a cover for the open¬ 
ings in the large tube. This 
short tube may be raised 
directly upward, thus uncov¬ 
ering the openings. 

The distributor is the same 
as that used in all the West- 
inghouse systems, in which 
a circular carbon brush 
makes contact with the va¬ 
rious high-tension terminals 
which are included in the 
molded cover. One terminal 
of the secondary winding of 
the induction coil is con¬ 
nected to the carbon distrib¬ 
utor brush by a metal ring 
mounted on a disk of insula¬ 
tion directly above the coil. 

The carbon brush extends through the end of the distributor arm 
and rests on the upper surface of the metal ring, which is con¬ 
nected electrically to the end of the secondary winding. 

The ignition switch is of the snap type and combined with the light¬ 
ing switch in one plate, which is mounted flush on the dash. Each time 
the ignition circuit is closed the polarity of the circuit is reversed. 

In adjusting the breaker the contacts should be dressed with 
a fine file and adjusted so that the maximum opening is .008 inch. 
A feeler gage is furnished with each outfit by the makers. The 



Fig. 359 —External view of West• 
inghouse unit 





422 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


spark-plug gaps should be .025 inch. The distributor brushes 
should slide freely in their holder, and the spring should push the 
top brush out to extend from the holder about *4 inch when the dis¬ 
tributor plate is removed. The only lubrication required is two 
or three drops of oil about once a month in the oil cup on the side 
of the distributor unit. 


What is termed a ballast coil is mounted in the back of the 
switch plate. This ballast coil is a small resistance in series with 
the primary winding of the coil, and its function is to protect the 
winding and prevent excessive drain on the battery should the 

engine happen to re¬ 
main idle with the 
switch in the “on” 
position. If this coil 
should be broken the 
ballast terminals may 
be short - circuited 
temporarily with a 
piece of wire or with a 
standard 5-a m p e r e 
fuse. An external 
view of the device 
complete is shown in 
Fig.. 359. 

Philbrin 

The Philbrin igni¬ 
tion system, manu¬ 
factured by the Phil- 
ips-Brinton Co., is 
both a single- and 
continuous-spark sys¬ 
tem. Either type of ignition may be used at will. The inter-rela¬ 
tion of the various parts of the combined breaker-distributor unit 
is shown in Fig. 360. The distinctive feature of the system is the 
breaker, which supplies a single spark of great intensity, the 
quality of the spark remaining practically the same for all engine 
speeds. 



Fig. 360 — Inter-relation of parts in Phil- 
brin system 


The construction of the .breaker is shown in Fig. 361 and its 
operation in brief is as follows: Rotation of the cam C, which 
is in effect a series of tiny triggers, pushes out the arm A, thus 












BATTERY-GENERATOR IGNITION 


423 


closing the contacts, which normally are open. When a trigger 
passes the arm the contacts are separated by the spring S in¬ 
stantly. The contacts are held together for approximately 3 y% 
degrees of the revolution of the cam. It is this breaker mechanism 
that gives the single spark. If the cam is rotated the wrong way 
the triggers simply push the arm A out of the way, it being 
mounted in a specially-shaped hole in its supporting member, as 
shown in Fig. 362. The continuous spark is controlled not by the 
breaker mechanism but by a tiny vibrator of special form con¬ 
tained within the switch assem¬ 
bly. 

The vibrator operates at four 
to five times the speed of the 
ordinary vibrator. As long as 
the engine is running a continu¬ 
ation of sparks is produced, and 
this stream is distributed, as are 
the sparks from the single-spark 
portion of the system, by the 
distributor mechanism. The dis¬ 
tributor has a long arm with a 
blade of peculiar form. This 
blade does not touch the high- 
tension terminals molded into 
the Bakelite cover but passes in 
very close proximity to the ter¬ 
minals, and the spark jumps a 
small air gap. The reason for 
this long blade is to insure a continuous stream of sparks at the 
plug during a considerable portion of the piston travel. This 
stream of sparks is an advantage when the engine is cold or the 
carbureter is slightly out of adjustment, for it practically insures 
firing the mixture. 

The Philbrin switch provides for two sources of current, the 
usual storage battery and an auxiliary set of dry cells, the arm 
of the switch being moved in ofie direction for the storage bat¬ 
tery and in the opposite direction for the dry cells. The lever 
which controls the operation of the continuous-spark and single¬ 
spark operations is a small continuously rotary plug. This plug 
is marked alternately M and S, signifying whether the main or 



Fig. 361 —Top view of Philbrin 
breaker mechanism 






















424 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

secondary systems are in operation. This special switch also re¬ 
verses the polarity of the circuit each time it is turned, thus 
increasing the life of the contacts. The ignition coil is mounted 
in a waterproof case and may be mounted on the dash or, in some 
installations, directly with the distributor mechanism. 

The system has but one adjustment, and this has to do with 
the opening of the contacts on the main, or single-spark, system. 

The gap between the contacts 
should be from .025 to .030 inch. 
The method of making the ad¬ 
justment is obvious from an in¬ 
spection of Fig. 362. The vi¬ 
brator for the secondary sys¬ 
tem is housed in the switch as¬ 
sembly and will never require 
any adjustment. The manufac¬ 
turers strongly urge that it 
never be touched. An external 
view of the Philbrin combined 
breaker distributor unit ia 
shown in Fig. 363. 


Delco System 

The earlier ignition systems 
manufactured by the Dayton 
Engineering Laboratories Co. 
operate on the open-circuit prin¬ 
ciple. A top view of one of 
the interrupters is shown in Fig. 364, and its operation is as 
follows: The movable contact is carried on a straight spring 
blade C, to which there is attached a bent spring blade B, 
held against the surface of the cam by the coiled spring E. 
The spring C is placed, when properly adjusted, under a slight 
tension due to the action of the springs B and E, and the movable 
contact on the spring C is held away from the stationary contact 
D. When the projection on the spring B strikes the projections 
on the cam, the end of C moves toward the stationary contact and 
the contacts close. As the projection on the spring B passes the 
hump on the cam, the action of the spring E draws B back sud¬ 
denly and the end of B strikes C and the contacts are quickly 




Fig. 362 —Operation of Pliilbrin 
breaker mechanism 

















BATTERY-GENERATOR IGNITION 


425 


opened. The duration of the contact, of course, will depend upon 
the speed of the cam, which, of course, depends upon the speed of 
the engine. 

In the later models of the battery ignition systems manufactured 
by the Dayton Engineering Laboratories Co. the closed-circuit 
principle is employed. A top view of the interrupter is shown in 
Fig. 365, and its operation is as follows: The arm B carries the 
movable contact D, which is 
normally in contact with the 
contact C. A piece of fiber is 
mounted on the arm B, which 
bears against the surface of the 
cam and is lifted by the projec¬ 
tions of the cam against a small 
flat spring which is held by the 
inner wall of the housing. The 
stationary contact C is adjusted 
by the screw and held in place 
by the lock nut N. These con¬ 
tacts should be so adjusted that 
when the fiber block mounted on 
B is on top of one of the humps 
on the cam, the contacts should 
open sufficiently to allow the 
gage on the wrench, provided with the system, to close the gap. 
The method of using the gage in adjusting the contact points is 
shown in Fig. 366. 

The timing of the spark may be adjusted by moving the cam A 
with respect to the shaft upon which it is mounted, which is done 
by loosening a screw in the end of the shaft and again tightening 
it after the cam has been moved the desired amount. Turning the 
cam in a clockwise direction, or toward the right, advances the 
time of ignition, and counter-clockwise, or to the left, retards it. 

Function of the Resistance Unit 

Should the ignition switch be left closed when the driver leaves 
the car, there is a likelihood of the contacts on the interrupter 
being left in the closed position, and if these contacts are closed, 
the battery will continue to discharge, which will result in its 
being completely exhausted if the discharge is allowed to continue 



Fig. 363 —External vieiv of Phil- 
brin combined breaker-distributor 
unit 


426 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

for a sufficient time. To prevent this waste of energy and possible 
damage to the coil, a resistance has been introduced into the pri¬ 
mary circuit. This resistance unit is shown in the upper left hand 
corner of Fig. 367. The unit consists of a small open coil of high 
resistance wire wound upon a porcelain spool. All the current 
passes through this resistance unit, but owing to the extremely 


Fig. 364 —Top view of Delco open-circuit type of 
interrupter 

short period it continues between interruptions, due to the opening 
of the contact points, the resistance wire remains fairly cool. 
When the ignition switch is left closed and the engine stops with 
the interrupter contacts closed, the current is then continuous and 
of greater effective value, and it causes the resistance wire to 
become heated to a red heat in a very short time. At this high 
temperature the resistance of the wire is much greater than at a 
lower temperature, so that it does not permit as much current to 
pass through the primary winding of the coil as would pass if the 
resistance of the wire remained unchanged. 

Delco Dual Type of Interrupter 

A dual type of interrupter is shown in Fig. 368. It has two 
independent sets of interrupter contacts, one for the battery and 







BATTERY-GENERATOR IGNITION 


427 


one for the magneto. The operation of this interrupter is the same 
as the other types except an additional set of contacts is provided. 

The earlier Delco ignition systems were provided with a way to 
produce a series of sparks for starting and a single spark when 
running. This device is no longer a part of their standard equip¬ 
ment, but its wide use on the thousands of cars at the present time 
warrants a description of its operation. The relay and a diagram 
of its connections are shown in Fig. 369. It consists of an electro¬ 
magnet provided with two windings, one of large wire and one of 
small wire, similar to the cutouts. The magnetic effect of the 



Fig. 365 —Top vieio of Delco closed-circuit type of 
interrupter 


coarse wire is greater than the magnetic effect of the fine wire, and 
it exerts sufficient magnetic pull on the armature when at rest to 
draw the armature toward the end of the armature core, which 
breaks the contacts at C. 

The construction is such that the current ceases to flow through 
the winding when the contacts C are open. The fine winding is 
connected to the contacts so that it holds the armature of the 
relay open after the circuit of the coarse winding is broken at the 
contacts C, and this winding is known as the “holding coil.’ 7 The 
magnetic pull of the fine winding is not sufficient to draw the 







428 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


armature down from the position of rest, but is strong enough to 
hold it down after the coarse winding has pulled it down. The arc 
at the contact C is suppressed by the condenser, which also in¬ 
creases the speed of operation. A three-way switch is provided, 
which has a point for starting and one for running and a neutral 
point. When the switch is thrown to the starting point, the relay 
operates continuously just the same as a vibrator and produces a 
series of sparks; when the switch is on the running point, the fine 
winding is energized and a single spark is produced. 

A special interrupter is provided for extremely high-speed en¬ 
gines. These interrupters are provided with two sets of contacts 
and a special cam, depending upon the number of cylinders. Each 


Fig. 360 —Method of using gage in adjusting contact points 
of Delco interrupter 



set of contacts is provided with a separate relay, and the circuit is 
closed through the two relays alternately, thus giving each mag¬ 
netic interrupter more time in which to open and close the circuit. 
The connections of a system of this type are shown in Fig. 370 
and a complete wiring diagram is shown in Fig. 371. 

Connections and Adjustments of Delco Ignition Relay 

Two methods of connecting the Delco ignition relay are shown 
in Figs. 371 and 372. In Fig. 371 the relay winding of large wire 
and the contacts shown at C in Fig. 369 are in series with a set of 




BATTERY-GENERATOR IGNITION 


429 


interrupter contacts on the dual interrupter. When the interrupter 
contacts are closed, a current is produced by the dry cells in the 
coarse winding of the relay, and its armature is drawn down, which 
cause the primary circuit to open and thus produce a spark at the 
plug. The armature of the relay is disengaged as soon as the 
contacts at C are opened, and the armature will continue to vibrate 
indefinitely as long as the interrupter contacts are together, unless 
the fine wire winding of the relay is energized in some way. The 
fine wire winding of the relay will not be energized if the switch 
connecting points 6 and 7 is depressed, and a series of sparks will 



Yig. 367 —Delco interrupter with resistance unit 

be produced so long as the interrupter contacts are closed. Thus in 
starting the switch which normally connects the points 6 and 7 will 
be held in an open position. 

The method used in connecting the Delco ignition relay on what 
was called the Junior system for 1914 is shown in Fig. 372. The 
ignition switch completes the primary circuit, and when the relay 
is used in this manner, the holding coil circuit is completed through 
the interrupter contacts. A vibrating spark is obtained as long as 
the timer contacts are open, and the timing of this vibrating spark 










430 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


is obtained by the action of the contacts upon the holding coil it¬ 
self. This method of using the relay causes much later ignition 
than the method previously described. 

When the armature B, Fig. 389, is pressed down, there should be 
absolutely no motion of the blade G, Fig. 373, carrying the lower 
contact. The gap at C should be approximately .005 in. When 
the blade A is lifted carefully By hand, the contact at C should 



Fig. 368 —Delco dual type of interrupter 


open to the same gap as before, namely, .005 inch. The contacts 
at C should be clean and their surfaces perfectly parallel. 

There are two adjustments to the relay, as follows: The air gap 
1 shown in Fig. 369, which increases the distance at C also, and the 
tension exerted by the spring A, Fig. 373, on the contacts C. Small 
adjustments may be made in the gap between the contacts at C, 
but in no case should this distance be increased very much over 






















BATTERY-GENERATOR IGNITION 


431 


.005 inch. If adjustment of this gap does not give a spark of suffi¬ 
cient intensity, it will be necessary to increase the tension of the 
spring. The tension in the spring can be increased by crowning as 
follows: The spring is held loosely between the jaws of a pair of 
duck-bill pliers near the end, which is screwed down to the frame, 



Fig. 3G9 —Delco ignition relay and internal connections 


and the pliers then are moved along the spring with a downward 
pressure and a slight twist to the right as shown in Fig. 373. This 
operation, properly performed, will give the spring the form shown 
in Fig. 374, and the tension will be increased noticeably. Be sure 
the armature is free on its pin. 





































432 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. S71 —Wiring diagram, of Delco ignition system with dual 
interrupter and ignition relay 













































BATTERY-GENERATOR IGNITION 433 

Delco Distributors 

Typical Delco distributors for four-, six-, eight- and twelve-cyl¬ 
inder installations are shown in Figs. 375, 376, 377 and 378. The 
one shown in Fig. 375 is used on the 1917 Dodge Brothers car; 



connections 

the one shown in Fig. 376 is used on the 1917 Hudson; the one 
shown in Fig. 377 is used on the 1917 Cadillac, and the one shown 
in Fig. 378 is used on the 1917 Packard. 











































434 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



To Distributor. 




Fig. 370 —Delco special interrupter for high-speed engines 



Fig. 373 —Method of crowning spring on Delco ignition relay 



Fig. 374 —Proper appearance of springs on Delco relay 


Single Ignition System 

The single ignition system, as its name indicates, is a systen) 
of ignition employing only one source of electrical energy, one 








































































BATTERY-GENERATOR IGNITION 435 

set of electrical connections and one set of spark plugs in the 
engine cylinders. The source of the electrical energy may be 
any of the various sources used in the different ignition systems, 
such as dry or storage battery and low-tension or high-tension mag- 


Figs. 375 to 378 —Typical Delco distributor installations. Fig. 

375, upper left, 1917 Dodge; Fig. 376, upper right, 1917 Hudson; 
Fig. 377, lower left, 1917 Cadillac, and Fig. 378, lower right, 1917 

Packard 

r.cto. A good example of a single ignition system is found on the 
Ford car as it is delivered by the manufacturer. Energy for igni¬ 
tion in this case is derived from a special form of low-tension mag¬ 
neto and is increased in intensity or pressure by a vibrating coil 
.from whence it is distributed to the various cylinders. In this par- 




436 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ticular case no distributor is used in the high-tension circuits or 
leads to the various spark plugs, but the interrupter, or timer, 
in the primary circuit serves as a distributor. An amplified 
diagram of the Ford ignition is shown in Fig. 379. When a bat¬ 
tery is installed this system then becomes a dual system as will 
be explained later. 

The single ignition system must not be confused with the term 
single-unit system. The single-unit system is one in which the 


-low tension Wires 

— HIGH TENSION WIRES 

-GROUNDED WIRE 

- ri - WIRE JUMPS ANOTHER 



Fig. 379 —Wiring diagram of single ignition system as 
used on Ford cars 


starting, generating and ignition operations are performed by 
one unit. In such a system the same armature fields are used 
for both the generator and the motor but a separate winding 
usually is employed for each of the two functions. The generator 
supplies energy for charging the storage battery, which in turn 
is used for ignition and operating the starting motor. 













































BATTERY-GENERATOR IGNITION 


437 


Dual and Double Ignition 

The various magneto and battery systems of ignition may be 
combined into what are called dual and double systems. A four- 
cylinder engine is shown equipped with four different systems of 



Fig. 380 —Four high-tension ignition systems installed 
on one four-cylinder engine 


ignition in Fig. 380, and a brief description of these different 
systems will be given before their various combinations are ex¬ 
plained. 

A high-tension magneto is shown toward the front end of the 
engine with its high-tension wires leading from the distributor to 
the four spark plugs marked Ml, M2, M3 and M4 respectively. 
From the terminal on the end of the magnets, marked B2, a wire* 
MG runs to the switch SI mounted on the vibrating coil. A sec¬ 
ond wire GG runs from this switch to the frame of the car, and 
if the switch is opened the terminal B2 will be disconnected from 
ground and the high-tension magneto will supply ignition current to 
the set of spark plugs to which its high-tension wires are connected. 

A high-tension battery system provided with timer and vibrat¬ 
ing coils for each cylinder also is shown, and the circuits may 
be traced as follows: Starting with the positive terminal of 

































438 


ELECTRICAL EQUIPMENT OF .THE MOTOR CAR 


the battery pass along the wire L to the switch S on the 
vibrating coil, then through the different primary windings and 
vibrators and along the wires LI, L2, L3 and L4 to the head of 
the timer, and from the center of the timer head along the wire G 
to the negative terminal of the battery. The high-tension wires 
lead from the under side of the vibrating coil to the four spark 
plugs HI, H2, H3 and H4, respectively, which are mounted in 
this case in the top of the engine cylinders. If the switch S is 
closed, current will be supplied to the different primary windings, 
in turn depending upon the order in which contact is made in 
the timer. The vibrator in each primary circuit will produce a 
series of sparks in the secondary circuit as long as the timer 
circuit for that particular primary circuit is closed. 

A third system consists of a low-tension magneto in combina¬ 
tion with a non-vibrating coil, and the circuits of this system 
may be traced as follows: Wires PI, P2 and P3 connect the 
armature winding of the low-tension magneto to the non-vibrat¬ 
ing coil and one terminal of the secondary wiring to ground, and 
if the switch on the front of this coil is thrown to the position 
marked M a circuit will be completed through the primary wind¬ 
ing of the coil. The wire P connects one terminal of the sec¬ 
ondary winding of the non-vibrating coil to the center terminal 
of the distributor on the low-tension magneto. The low-tension 
current of the magneto will pass through the primary winding 
of the coil and when it is interrupted suddenly by the breaker 
oil the magneto a high-tension current will be produced in the 
secondary winding, which will supply energy to one of the spark 
plugs, depending upon the position of the distributor contact or 
arm. A fourth system is provided which is identical to the one 
just described with the exception that the battery replaces the 
winding on the magneto. 

If the first two or the last two systems just described were 
combined we would have what is called a dual system. In each 
of these dual systems the same set of spark plugs and high- 
tension distributors are used. Other combinations, of course, may 
be used in forming a dual system. 

If the vibrating coil, timer and battery, with spark plugs, HI, H2, 
113 and 114, and the high-tension magneto, with its spark plugs, 
Ml, M2, M3 and M4, were combined on a single engine, the com¬ 
bination would be called a double system. A second double system 


BATTERY-GENERATOR IGNITION 


439 



Fig. 381 —Double ignition system using a Mgli-tension magneto 
with a vibrating coil timer and battery 


IGNITION CO/L 


SET. 2. 



DISTRIBUTOR FOR 
SPARK PLUGS 
SET.l. 


DRIVE END 


CONTACT BREAKER 1 


Fig. 382 —Wiring diagram of Remy in which two sparJcs are provided 
for igniting the gas at the same time 


















































































































440 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

could be formed by combining the low-tension magneto, non-vibrat¬ 
ing coil, timer and plugs Ml, M2, M3 and M4 with the vibrating 
coil, timer and battery and plugs III, H2, H3 and H4. Other com¬ 
binations are used for combining the various single ignition systems 
into dual and double systems. The wiring diagram of a double 
system using a high-tension magneto in combination with a vibrat¬ 
ing coil timer and battery is shown in Fig. 381. 

Two-Spark Ignition 

Two-spark ignition simply means that two sparks are provided 
for igniting the gas mixture in the cylinder at the same time, 
the object being to increase the power and speed. Magnetos used 
in providing two-spark ignition usually are provided with two 
separate distributors and in some cases with two windings served 
by a common breaker. The wiring diagram on a Remy two-spark 
magneto is shown in Fig. 382. 


CHAPTER XXIV 
Spark Plugs 

T HE spark plug is one of the most important parts of the igni¬ 
tion systems, and no matter how carefully the remainder of 
the system is constructed and installed the successful opera¬ 
tion of the system is entirely dependent upon the spark plug. 
The spark plug is a very simple device which consists of two ter¬ 
minal electrodes carried in a suitable shell, which is screwed into 
an opening provided for it in the cylinder w’all. A section of 
several typical spark plugs are shown in Fig. 383. The secondary, 
or high-tension, wire from the ignition device is connected to a 
terminal at the top of the plug, which usually forms the central 
electrode and extends down through the plug. This center mem¬ 
ber is insulated from the shell by a bushing of some form of 
insulating material. The electrode and bushings are fastened in 
a steel shell or body, which is provided with a threaded end at 
the bottom, by which it may be fastened into the wall of the 
combustion chamber. The insulating materials commonly used 
are porcelain, mica, steatite and lava. Porcelain and mica are 
used more than other insulations, because their mechanical and 
electrical characteristics make them better suited for this. When 
porcelain is used some form of insulating packing must be used 
to keep it from contact with the metal shell of the plug. This 
packing is required, because the porcelain and steel have different 
coefficients of expansion and it is absolutely imperative that some 
flexibility be provided at the joints to permit the two materials 
to expand differently when heated. 

In the early forms of spark plugs the insulating material filled 
the shell at the lower, or sparking, end of the plug, which afforded 
a direct path for the current to travel over just as soon as this 
small surface was coated with carbon. It was nothing uncommon 
to have to clean this type of plug in less than 100 miles of running. 


442 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

This objectional feature was greatly improved by allowing a space 
between the insulation surrounding the central electrode and the 
outer shell. 


Arrangements of Electrodes 

The arrangement of the electrodes varies considerably and may 
take the form of open points as in Fig. 384, a bridge as in Fig. 385, 
several points as in Fig. 386, an inclosed arrangement as in Fig. 
387, etc. Certain advantages are claimed for the plugs provided 
with more than one gap. This advantage, however, is more theo¬ 
retical than practical, since the electrical current will bridge the 
gap offering the least resistance and should one of the gaps be¬ 
come shorted, by a particle of carbon, all of the gaps will be 
shorted. 


Series Spark Plug 

In the series type of spark plug the spark occurs between two 
central electrodes each of which is insulated from the shell of the 
plug. A plug of this type is shown in Fig. 388. The objects of such 
a plug is to furnish a means of providing two sparks in each 
cylinder by a standard ignition system. A plug of this type and 
a standard type of plug are mounted in the wall of the combus¬ 
tion chamber. The high-tension wire from the ignition system is 
connected to a terminal of the series plug, and the second ter¬ 
minal is connected to the central electrode of the standard plug, 
thus connecting the gaps in the plugs directly in series. The 
object of such an arrangement is to provide double-spark igni¬ 
tion. Experiment has shown a slightly increased power when two 
sparks occur simultaneously in different parts of the combustion 
chamber, especially in the T-head type of engine cylinder in which 
the two plugs can be located over the oppositely-placed valves. 
As the great majority of engines are of the L-head type and since 
the advantages of the series type of spark ignition at best are so 
very slightly greater than the single-spark type, there is very 
little advantage to be gained in its use. 

The series type of spark plug may be used as a grounded returr 


SHARK PLUGS 


443 

type by an attachment as shown in Fig. 289. All this attach¬ 
ment does is to form a metallic connection between one of the 
terminals or electrodes and the shell of the ping which is, of 



Fig. 383 — A section of typical spark plugs, shotcing, upper left, 
typical ends; upper right. Red Head; lower left, Kingston, Su-Dig 
and Master; and lower right, Splitdorf 


course, in electrical contact with the engine cylinder. The high- 
tension ignition lead, of course, is connected to the terminal on 
the spark plug to which the special attachment is not connected. 





















444 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


Magnetic Type of Plug 

This type of spark plug was developed with a view to overcom¬ 
ing the trouble in the operation of the make-and-break plug as 
used on the low-tension ignition systems. A section through a 
plug of this type is shown in Fig. 390, and its operation is as 
follows: A solenoid, A, surrounds a plunger, C, whose lower end 
is held in contact at D, by a spring, B. The magnetic pull due to a 
current in the winding A lifts the plunger and causes a spark at 
D. Plugs of this type have found little use on the motor car, as 
the high temperatures to which they are subjected in such applica¬ 
tions draw the temper of the plunger spring and often seriously 



Fig. 383 continued—Other typical spark plugs, respectively 
Bosch, AC and Blits 


injure the insulation of the solenoid winding. Their use has been 
more extensive in connection with stationary engines where the 
temperatures are much lower. 

Waterproof Plugs 

In certain applications of the gasoline engine, as on motor boat 
engines in particular, the spark plugs are likely to become short- 
circuited from the spray or dampness. A special plug is pro¬ 
vided to prevent such an occurrence, and a plug of this type is 
spoken of as a waterproof type. The only difference in the con- 





SPARK PLUGS 


445 



struction of a plug of this type and the ordinary plug is the addi¬ 
tion of a protective hood of hard rubber or other suitable insula¬ 
tion placed over the connections. A plug of this type is shown in 
Fig. 391. 

Priming Plugs 

The priming type of spark plug is one provided with a pet 
cock as shown in Fig. 392. This plug usually is used on engines 
which are not regularly equipped with priming or compression- 
release cocks. 

Airplane Type 

The construction of the airplane type of spark plug anticipates 
the development of great heat. A plug designed for this particu- 


Figs. 384 and 385 —Champion Fig. 386 —Electrodes with sev- 

electrode of open points, left, eral points on the Stewart V- 

and Center Fire bridge Ray and Bosch 

lar use is shown in Fig. 393. The insulation core C is built up of 
mica washers and has square shoulders. These square shoulders 
afford two gasket seats, and when the core is clamped in the 
shell by the check nut E it is centered accurately and a tight 
joint is formed. This construction gives a plug shorter than 
with conical fits and thus improves the heat radiation through the 
stem. The lower end of the shell has a baffle plate, O, which 
tends to keep oil from the mica. Perforations, L, in the baffle 


















446 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


plate prevent burnt gases from being pocketed behind the plate 
and pre-igniting the charge. The stem P is made of brass or 
copper for superior heat conductivity, and the electrode J is 
swedged in the bottom of the stem, as shown at K. The shell is 
finned, as shown at G, to provide greater heat-radiating surface. 
A fin, F, at the top of the stem also increases the radiation of the 
heat from the stem and electrode. The top of the fin and portion 
is countersunk slightly, and the stem is riveted into it, thereby 
preventing leakage past the threads on the stem. The finned por¬ 
tion is necked at A to take a slip terminal. In building up the 



Fig. 387 —Plugs ivith inclosed Figs. 388 and 389 —Efficiency spark 
arrangement, the Reflex and plug and special attachment for series 
D & D Fouless spark plug 


core a small section of washers, I, is built up before the mica in¬ 
sulating tube D is placed on. This construction gives a better 
support for I. The baffle plate O is bored to allow the electrode 
J to pass through, and the clearance between the baffle plate and 
the electrode is larger than between the firing joints, as there is 
no danger of spark jumping from electrode to baffle plate. This 
plug is supplied with or without the finned portion. 

Plug Threads 

The straight-threaded plug is standard European practice. The 
tnread itself is usually fine pitch. This type of plug is screwed 



















SPARK PLUGS 


447 


in tight against a gasket of copper or asbestos to prevent break¬ 
age. Foreign-made plugs usually are referred to as metric plugs, 
as the thread dimensions are based on the metric standard. 

All spark plugs in this country were made first with an iron- 
pipe thread, which has a taper of % inch to the foot, and tne 
plug is screwed into the cylinder as far as the taper will permit, 




Fig. 390 , left—Magnetic type 
of spark plug. Fig. 391 , upper 
left—Waterproof type of spark 
plug. Fig. 392 , upper right — 
Priming type of spark plug 


no gasket being used to hold the compression. This is not alto¬ 
gether satisfactory, and since the metric 3 ystem is not used 
very extensively in this country, a separate type has been de¬ 
veloped and is known as the S. A. E. standard plug. The diame¬ 
ter and thread on this plug both are somewhat larger than those 
used abroad. 

The S. A. E. standards for spark-plug shells are illustrated in 
Fio\ 394. All dimensions below the shoulder are identical for both 
siz & es of spark-plug shells. The spark plugs can be turned in by 













































448 'ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

hand, using a wrench only for final tightening, if the taps are 
made to dimensions as follows: Diameters, nominal dimensions, 
outside, A, .875 in.; pitch, B, .839 in.; root, C, .803. 



Fig. 393 —Airplane type of spark plug t the Pitts¬ 
fieldj showing the structure in cross section 



Fig. 394 — 8. A . E. standard dimension for spark-plug shell 9 















































































SPARK PLUGS 


449 


The spark plugs should be placed in the wall of the combus¬ 
tion chamber in such a position, when possible, that the spark 
produced between the electrodes will be directly in the path 
of the entering fresh gases from the carbureter. Several meth¬ 
ods of installing spark plugs are shown in Fig. 395. In the 
cut marked A the plug is screwed into a threaded hole in the 
valve cap, and in this particular case the electrodes of the plug 
are in a pocket. In the cut marked B the position of the spark 
plug has been lowered by cutting a recess in the top of the valve 
cap, which allows the electrodes of the spark plug to extend 
down so there is ample clear space around them. The installation 
shown at A is much more troublesome than the one shown at B 
due to the fact that the electrodes are more likely to become 
short-circuited by accumulation of oil or carbon, and some of 
the burned gases may remain in the pocket and thus prevent the 
fresh mixture from the carbureter from getting in around the 
spark gap. 

The two mountings shown in cuts C and D are practically the 
same so far as the position of the spark gap in relation to the 
combustion chamber is concerned, but their mechanical mounting 
in the cylinder wall differs. The method of mounting shown at C 
does not permit the heat to be transferred as readily to the cooling 
jacket as the installation shown at D, and hence the plug shown 
at D will be somewhat more efficient. 



Fig. 395 —Several methods of installing spark plugs 

Spark Plug Terminals 

Every spark plug should be provided with some form of termi¬ 
nal at its outer end by which the end of the high-tension wire 
may be connected electrically to the insulated electrode of the 
spark plug. This terminal, as found on spark plugs at the present 
















450 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

time, assumes several different forms, but they must all meet one 
main requirement, that is, the electrical connection must be made 
securely so there is no chance of an open circuit at this point. 
The chief difference in the design of the different terminals is in 
the manner of fastening the wire or terminal on the end of the 
wire to the plug. 

Gap Between Electrodes 

The gap between the electrodes of a spark plug should be ad¬ 
justed to approximately 3*2 inch for spark plugs used with battery 
ignition system, and to approximately half this amount, or 
inch, for spark plugs used with magneto ignition systems. Several 
companies provide a thickness gage to use in adjusting the dis¬ 
tance between the electrodes so that the best results may be 
obtained with that particular system. The space between the 
terminals of the electrodes of the spark plug offers a very high 
resistance to the flow of electricity until sufficient pressure has 
teen applied to produce an are between the electrodes, which 
greatly lowers the resistance. This arc will not be produced 
unless sufficient pressure is applied. The pressure required to 
pi’oduee an arc between the electrodes of a spark plug depends 
upon the distance between the electrodes and the degree of the 
pressure of the gas in the combustion chamber in which the spark 
plug is mounted. The pressure required also depends upon the 
form of the electrode, that is, whether it is round, square, pointed, 
etc., at the end. The larger the gap between the electrodes, etc., 
the greater the electrical pressure required; likewise, the greater 
the pressure in the combustion chamber the greater the electrical 
pressure required to produce an arc. A spark plug which may 
appear to give a very good spark when it is tested outside the 
cylinder may not work at all satisfactorily when placed in the 
cylinder due to the high pressure in the cylinder. 


CHAPTER XXV 


Ignition Wiring and Timing 


HE wiring for an ignition system may be divided into two 



1 main groups, low and high-tension wiring. The wires for the 
low-tension circuits are subjected to a relatively low voltage, and 
the insulation surrounding them need not be very thick to prevent 
serious leaks of electricity, which would reduce greatly the effi¬ 
ciency of the ignition system. On the other hand, the wires used 
in the high-tension circuits are subjected to a high voltage, and 
the insulation surrounding them must be of ample thickness and 
of such a character as to withstand easily this high voltage and 
thus confine the flow of the electricity to the path in which it is 
supposed to move, so that the ignition system may operate satis¬ 
factorily. The insulation used on the wires for both the low and 
high-tension circuits must possess ample mechanical properties, 
in addition to their electrical properties, to withstand the heat 
and mechanical abuse to which they will be subjected in ordinary 
use. The cross-sections of several of the different kinds of wires 
used in motor car wiring are shown in Fig. 396. 

Great care always should be exercised in placing the various 
ignition wires on the car, so they may be subjected to tffe minimum 
mechanical abuse of the shortest length possible, run in such 
places and so protected that they will not be seriously injured 
by water, oil or heat. 

The ends of all wires should be fastened securely at their ends 
to reduce to a minimum the likelihood of a loose connection or 
open circuit. 


Timing Battery System 


There is a difference between the time when the spark is made 
between the electrodes of the spark plug and when the combus¬ 
tion of the gas actually takes place. If the combustion of the gas 


452 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

mixture in the cylinder actually took place at the same instant 
the spark in the combustion chamber was produced then the 
proper place to set the timing mechanism would be that position 
which would cause the spark to occur at the top of the compres¬ 
sion stroke of the piston in its travel up and down in the cylinder. 
There is, however, as stated above, a certain amount of time 
required for the gas mixture to burst into full explosion after 
the ignition spark occurs, but it is desirable to have the spark 



Fig. 396 — Cross-sections of wires and cables used on motor cars 


occur at such a time that the full combustion of the gas will take 
place when the piston is at the point of highest compression. 

There are two main points to consider in setting the time of 
spark in relation to the position of the piston in its travel in 
the engine cylinder and these are: First, the kind of ignition sys¬ 
tem and, second, the speed at which the engine piston is traveling. 

If a coil and vibrator system of ignition is used, it is no more 
than natural to suppose that the actual time in making contact 
at the commutator and the time of action the vibrator will be 
greater than if a single contact system is used as in the case of 
the magneto or single-spark system. Hence, it is necessary to set 






IGNITION WIRING AND TIMING 


453 


the spark so it will occur a longer time before the top of the 
compression stroke than will be necessary when an ignition sys¬ 
tem that is less sluggish in action is used. 

When the speed of the piston is low, or the engine is running 
slow, the time required for the piston to travel from a given point 
to the point of maximum compression will be considerably greater 
than the time required for the piston to travel the same distance 
when the piston is traveling at a higher rate or the engine is run¬ 
ning fast. It readily is seen that the time the spark occurs in the 
engine cylinder in relation to the position of the piston must be 



changed as the speed of the engine changes. As the engine speeds 
up the spark should be caused to occur at an earlier time in relation 
to the position of the piston so there will be a full combustion of 
the gases in the engine cylinder when the piston is at its extreme 
travel. In order that the spark may occur at a later time in 
relation to the position of the piston the contact or interrupter 
controlling the spark should be moved in the direction of rotation 
of the shaft driving it. In practice moving the interrupter or 
contact device in the direction the shaft driving it rotates is 
called retarding the spark, while rotating the interrupter or con¬ 
tact device in the opposite direction is called advancing the spark. 












454 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The meaning of these terms will be clearly understood by refer¬ 
ence to Figs. 397 and 398, which show the spark fully advanced 
and fully retarded. 

Space will not permit a complete description of the details 
of the method of timing all the various battery ignition systems, 
but the following main points must be kept in mind always. 
Make sure the contacts on your timer or the interrupter are oper¬ 
ating at the proper time in relation to the position of the engine 
pistons when the spark lever is in its two extreme positions. Make 
sure the contacts on the timer are connected to the proper primary 



coils when a coil is used for each cylinder and that the secondary 
leads from these coils are connected to the proper spark plugs 
so the firing order of the cylinders will be correct. Make sure 
the connections from the distributor to the various spark plugs 
are correct. Inspect all the connections and wiring for appar¬ 
ent cases of trouble. The reader is referred to the book of instruc¬ 
tions furnished by the manufacturer of the different cars for the 
details in setting the positions of the cam operating the inter¬ 
rupter or the timing contacts of the timer, etc. 









CHAPTER XXVI 


Electric Signals and Accessories 

D EVELOPMENT of starting, lighting and ignition systems has 
resulted in the installation on the motor car of a small elec¬ 


trical powerplant of considerable capacity, and, as a result, elec¬ 
trical energy is now available to a much larger degree than it 



Fig. 399 and 400— Buzzer-type electric horns in which the 
electro-magnet acts directly upon the diaphragm, left, and 
through the medium of a plunger, right 


was on the early cars, which usually were provided with a set 

of dry cells and at most a storage battery which had to be 

charged by removing it from the car. As a result of this, larger 

sources of electrical energy being available at all times, a great 

many useful electrical accessories have been developed to quite 
a high degree of perfection and add to the convenience and 
comfort in operating the car. Some of the more important of 
these electrical accessories are discussed briefly in the following 
paragraphs. 

Electrical Alarms 

Electrical alarms operate on two general principles: they 
may be of the buzzer type or of a mechanically-actuated dia- 



































456 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

phragm type. The operation of the first type may be understood 
readily by reference to Figs. 399 and 400. In Fig. 399 the dia¬ 
phragm is attracted directly by the electromagnet, while in Fig. 
400 the diaphragm, or sound-producing element, is vibrated by 
a plunger attached to an iron armature, which in turn is ac¬ 
tuated by the magnetic action of the electromagnet. 

In the mechanically-operated type the diaphragm, or sound- 
producing element, is operated by a ratchet wheel which may 
be made to revolve either by hand or by an electric motor, de- 



Fig. 401 — Right—Construction of mechanically-operated horn 
Fig. 402 — Left—Electric motor operated horn- 


pending upon its construction. The fundamental principle of 
the mechanically-operated horn is shown in Fig. 401. A glass- 
hard tooth wheel W is made to revolve and causes the button B, 
which is attached to the diaphragm, to vibrate. This toothed 
wheel may be in a horizontal position or parallel to the dia¬ 
phragm as shown in Fig. 402, which shows a cross-section of an 
electric motor used in revolving the wheel. The tooth wheel 
is carried on the same shaft as the armature M, and the end 
thrust is taken care of by an end thrust bearing at the left 
hand end. The adjustment of the horn is made by turning the 
screw S until the desired note is obtained when the horn is run- 
















ELECTRIC SIGNALS AND ACCESSORIES 457 

ning and then locking S in position by the nut A. The working 
parts are all inclosed by the cover C. 

The interior views of two different types of hand operated 
horns are shown in Figs. 403 and 404. The toothed wheel in 
the horn shown in Fig. 403 is driven by a spiral plunger which 
must be depressed by hand. Adjustment of tone in this case 




Fig. 403 —Cross section of Fig. 405 — Electrically - 

typical hand-operated horn operated lamp-hell 

is provided by varying the pressure in a spring in front of the 
diaphragm which presses the diaphragm against the toothed 
wheel. 

The toothed wheel in the horn shown in Fig. 404 is driven by 
a special bevel gear. The larger member of this gear is ro¬ 
tated by turning a handle on the back of the horn. The handle 
may be rotated in either direction. 

An unusual form of electric signal is shown in Fig. 405, which 
consists of an electrically-operated bell. The bell itself is cast 
from bronze and on top of it is mounted a smaller compartment 
containing a small electric lamp and provided with windows of 



458 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

polished ruby jewels. Inside the bell is an electromagnet which 
operates the clapper through special alloy contacts. The bell 



Fig. 404 —Exterior and interior of crank-operated horn 

is provided with a bracket for fastening it to the front of the 
radiator. 

Care of Electric Homs 

The care of the buzzer type of electric horn is practically the 
same as that given the electric cut-out and the regulators used 
with the generators. It will be necessary to clean and true 
up the contact points at intervals and it more than likely will be 
necessary to adjust the spring. A weak sound may be due to a 
discharged battery, open circuit, grounded circuit or lack of 



ELECTRIC SIGNALS AND ACCESSORIES 


459 


adjustment. An open circuit may be caused by a broken wire, 
poor contact in push buttons, loose connection or lack of adjust¬ 
ment in horn, which may result in the contacts not making con- 



Fig. 406 —Several forms of spotlights and mountings 

tact and no current can pass through the winding of the electro¬ 
magnet. 

In the motor-driven type of horn the commutator and brushes 
will require attention at more or less regular intervals, depend¬ 
ing upon the use that is made of the horn. A horn of this type 




































1 

460 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

may fail to operate due to a broken wire, grounded circuit, 
loose connection, dirty commutator, brushes not properly ad¬ 
justed, poor contact in contact button, or the battery may be 
exhausted. It may happen that the motor will run but the 
horn may produce a very weak sound or no sound at all and in 
such a case it is due to the poor contact between the toothed 
wheel and the button on the diaphragm. An adjustment may 
remedy this difficulty or it may be necessary to replace either 
the button or toothed wheel or both as they will wear out in 
time in spite of the fact that they are both made glass hard. 

Spot Lights 

The primary purpose of a spotlight is to afford a light which 
may be directed by the driver or other occupant of the car in any 

direction, independent of 
the direction in which the 
car is traveling. The spot¬ 
light consists of a para¬ 
bolic reflector provided 
with a suitable incan¬ 
descent lamp mounted in 
a containing case with a 
glass front and fastened 
to an adjustable bracket 
attached to some part of 
the car within easy reach 
of the party who is to 
control the direction in 
which the light from the 
lamp is to be thrown. 
Very frequently the spot¬ 
light housing is provided 
with a mirror by which 
the driver may be able to 
determine what is behind 
him while driving during 
the day, provided the 
spotlight is fixed in a 
definite position. The switch controlling the spotlight may be 
mounted in the handle on the housing or it may be placed on the 



Fig. 407 —One form of trouble 
lamp, lower, with light installa¬ 
tions 



ELECTRIC SIGNALS AND ACCESSORIES 


461 


cowl board or within easy reach of the operator. Several different 
forms of spotlights and brackets are shown in Fig. 406. 

Trouble Lamps 

The trouble lamp usually consists of a small reflector on the 
end of a convenient handle and provided with an incandes¬ 
cent lamp of proper voltage. A flexible extension cord is provided 
for connecting the lamp to one o‘f the lamp sockets on the car 
or one specially provided for the trouble lamp. One form of 
trouble lamp is shown in Fig. 407. In some forms a reel is 
provided upon which the extension cord may be wound. The 
reel usually is operated by a coiled spring which is under tension 
when the extension cord is pulled out. 




Fig. 408 —Two kinds of electric heating devices 


Electric Heaters 

The electric heater is a device in which electrical energy is 
converted into heat energy. A device of this kind frequently 
is used in keeping the engine warm and preventing the radiator 
from freezing in a cold garage. Two electric heaters for this 




4C2 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

purpose are shown in Fig. 408. The electric heater is sometimes 
installed in the intake manifold to get better carburetion and 
thus facilitate starting. A device of this kind is shown in 
Fig. 409. 

Signals and Direction Indicators 

Several different kinds of electric signals and direction indi¬ 
cators have been devised and perfected so that the driver of a 
car may give notice to those immediately behind of his intention 
to stop or turn to the right or left with a view to eliminating the 
danger of collision. Devices of this kind are shown in Fig. 410. 
The Warner device shown at A in the figure consists of a brass 
cuter housing with a rectangular opening cut out in the back side 
of it. Inside this brass shell there is a glass tube divided into 


BAOf Of SWITCH 



Fig. 409 —Manifold heating device, left , showing installation 

four sections. On one of these sections there appears in large 
letters the word STOP. Another section is colored plain red and 
the other two are labeled TURN with arrows pointing to the right 
and left respectively. Three electromagnets are mounted inside 
the brass shell at one end, and these magnets may be made to act 
upon an armature attached to the shaft upon which the glass tube 
is mounted. The position of the glass tube, of course, will depend 
upon which of the magnets is acting upon the armature, which 
in turn will depend upon which button or circuit is closed. In 
the cross-section shown, the armature is at the bottom where it 




























ELECTRIC SIGNALS AND ACCESSORIES 463 

tends to stay normally under the action of gravity, the magnets 
being de-energized. 

The Safety-Lite signal which is shown at B in Fig. 410, indicates 
the direction in which a car is going to turn by means of arrows. 
The device consists of a metal containing case containing electric 
bulbs which may be controlled from the dash or steering wheel. 
The light from the electric bulbs, depending upon which one is 
lighted, brightens either the right or left arrow so as to render it 
clearly visible to a driver in the rear. 

A third form of signal, called the Pomeroy, is shown at C in 
Fig. 410. This signal is provided with three solenoids. Two 
operate the swinging indicator lever so as to show L or R, and 
the third controls a shutter which normally hides the word stop 
from view. 



Fig . 410 —Several different types of signals 

There are many other forms of signals and direction indicators, 
but they all have a common purpose, and their operation should 
be made as near automatic as possible. For this reason in a great 
many cases, the electrical circuits controlling their operation are 
opened and closed by the driver in operating some part of the car, 






























































464 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

such as pressing the brake pedal, which will cause the word 

‘ 1 stop ’ ’ to appear on the signal board. 

• 

The Electric Brake 

The object of the electric brake is to provide an easily op¬ 
erated electrical means of applying the brakes on a car and 
thus do away with the manual labor usually connected with 
their operation. In the Hartford electric brake a high-speed 
series motor is used, and this motor may be wound so that it 
may be operated from any voltage source of electric energy 
available. For motor car work the more common voltages are 
6, 12 and 24 volts. The armature shaft of the motor carries a 



worm which engages a worm gear, the reduction being 100 to 1. 
This worm gear drives a drum through the medium of an internal 
gear at a reduction of 4 to T, which makes the total reduction 
from motor shaft to drum 400 to 1. The pull of the motor is 
transmitted to the brake mechanism by a steel cable one end of 























ELECTRIC SIGNALS AND ACCESSORIES 465 

which is attached to the brake equalizer and the other end winds 
on the drum. 

The motor is controlled by a special controller mounted within 
easy reach of the driver as shown in Fig. 411. The first point 
on this switch, which is a two-point affair, gives ample braking 
power for all ordinary requirements, while the second point gives 
a much greater braking power and is used in making emergency 
stops. Restoring the switch to its original position immediately 
disengages the brake. 

The motor used in operating the brake is capable of making 
10,000 revolutions per minute when running idle, and under load 
it can exert a pull of 100.0 pounds at a speed equivalent to a 
quick application of the hand emergency brake. A slipping 
clutch prevents the motor from exerting a pull in excess of 1000 
pounds, and a ratchet prevents the brake from slipping off. The 
powerful pull excited by the motor on the brake cable permits 
of operating the emergency brake in oil. The motor will take a 
current of 40 amperes for approximately two-fifths of a second 
from a 6-volt battery for each application of the emergency brake. 

Electric Vulcanizers 

The electric vulcanizer is a vulcanizer in which the heat is 
supplied by passing an electric current through a resistance unit. 
This resistance unit is mounted in half of the vulcanizer or in 
one of the plates. Thermostats are provided in some for auto¬ 
matically cutting off the current when the temperature has at¬ 
tained the correct value, and others have a thermometer opening 
or pocket into which a thermometer may be placed and the tem¬ 
perature observed. These vulcanizers are provided with flexible 
leads and are wound for different voltages ranging in value from 
6 to 110 and 220. 


CHAPTER XXVII 

Electric Gearshifts and Transmissions 

T HE electric gearshift is another valuable addition to the elec¬ 
trical equipment of the motor car which has been made pos¬ 
sible by the installation of a charging generator and a constantly 
changed storage battery. 

Four movements are necessary to engage all of the speeds in 
a standard three-speed forward and one speed, reverse gear of the 
selective type. These various changes are carried out as fol¬ 
lows: A sliding pinion is used for first and second speeds, a 
toothed clutch for the direct drive and an idler between two of 
the gears for giving the reverse speed. All of the preceding 
movements are accomplished by a yoke attached to the member 
being moved. The yoke is attached to a movable bar, which 
is in turn connected to the hand lever through a convenient link¬ 
age. The electrically-operated gear is identical to the one de¬ 
scribed and all the parts mentioned are retained with the excep¬ 
tion of the hand lever. The two movable bars to which the yokes 
are attached are lengthened somewhat, and their ends form arma¬ 
tures or cores for four solenoids. 

The principle of operation of the electric gearshift may be 
understood easily by reference to Fig. 412, which shows in a 
simplified diagrammatic form the operating electrical circuit, push 
buttons and solenoids. There are four solenoids, one for each 
movement necessary. If you press button 1 you close the circuit to 
solenoid 1, causing the movable bar A to move to the left. If 
you press button 2 you close the circuit to solenoid 2, causing 
the movable bar A to move to the right. If you press button 3, 
solenoid 3 is energized and the movable bar B moves toward 
the left, while if you press button R solenoid R is energized and 
the movable bar B moves toward the right. Pressing the button N, 
called the neutral button, and then throwing out the clutch neu- 


ELECTRIC GEARSHIFTS AND TRANSMISSIONS 


467 


tralizes the gears, that is, all gears are disengaged and the engine 
is no longer connected to the propeller shaft. 

The above buttons, which are mounted within easy reach of 
the driver, usually upon the steering post, when pressed do not 
entirely close the circuit to the respective solenoids but merely 



Fig. 412 —Principle of operation of electric gearshift in simplified 

form 


place the particular solenoid which they control in connection 
with what is called the master switch. These buttons themselves 
are referred to as selector switches, because they select in ad¬ 
vance the circuit and hence the solenoid which will be energized 
when the master switch is closed. The master switch is con¬ 
trolled by the clutch pedal, and it is closed when the clutch pedal 
is pushed down to the extreme position. The clutch pedal has 
ample movement so that the clutch may be disengaged without 
closing the master switch. 

In stopping the car the neutral button is pressed and the clutch 
pedal pressed all the way down. When the neutral button is 












































468 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

pressed, all the contacts which may have been closed previously 
by the selector switch buttons are broken, and depressing the 
clutch pedal then brings into action what is called the neutraliz- 


Fig. 413 —End view of Cutler-Hammer neutralizing 
device and master switch 


Fig. 414 —Plan view of Cutler-Hammer neutralizing 
device and master switch 

ing device. For example, if the car has been running on high and 
you desfre to stop, the neutral button is pressed and the clutch 
pedal pushed all the way down against the floor board. This 
causes the lever K, see Fig. 413, to move forward and then the 





ELECTRIC GEARSHIFTS AND TRANSMISSIONS 469 


neutralizing causes F to pull on the boss on the shifting forks 
as if a shift in gears were to be made, and the master switch M 
will also close. Since the neutral button has opened all of the 
selector switches, all the solenoids have no current in their wind¬ 
ing and the gears remain in neutral. A plain view of the neu¬ 
tralizing device and master switch are shown in Fig. 414, and 
two of the solenoids with their mountings, are shown in Fig. 415. 
The relative location of the different parts of the complete device 



Fig . 415 — Cutler-Hammer solenoids and container for electric 
gearshift 


are shown in the phantom view in Fig. 416. The solenoids are 
marked B 1, B 2, B 3 and B 4 and their respective cores are 
marked C 1, C 2, C 3 and C 4. 

In passing from one speed to another the operation is as fol¬ 
lows: The selector switch corresponding to the desired speed i3 
pressed and the clutch pedal is rotated all the way forward, 
which rotates the operating lever K and its shaft upon which 
the rocker arm I and its mechanism are mounted. The latch H 
is in engagement with the pawl G of the neutralizing mechanism, 
and as the operating lever and the rocker arm I are rotated, the 
latch H presses against the pawl G, causing both of the neutraliz¬ 
ing cams F to rotate toward the center a^ they are engaged 
through the teeth P. On the central side of the shifting fork D, 
Fig. 416, is a boss and as the neutralizing cams rotate they press 
against the boss on whichever side is in engagement, and the 



470 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

shifting fork and the gear with which it is engaged are pulled 
back to the neutral position before the next shift can be made. 
As the gear comes into the neutral position, the end of the latch 
H strikes what is called the knockout pin, which action releases 
the latch from engagement with the pawl G, and as the operating 
lever K is moved ahead by the lever pressing down on the clutch 
pedal, the switch operating pawl L pulls against the switch stem 



Fig. 416 —Phantom view of Cutler-Hammer electric gearshift 


and closes the circuit at the master switch. The gears may be 
changed by hand, should the battery become exhausted, by in¬ 
serting an emergency hand lever in the socket S and the gears 
changed in the usual manner. 

In starting, all gears are in neutral. The first thing to do is to 
press the first-speed selector switch which connects one of 
the solenoids to the master switch. Next depressing the clutch 
pedal all the way down rotates the lever K, see Fig. 413, through 
the connecting rod L which is attached to the clutch pedal. This 
operation pulls the blades of the master switch M into contact 
which completes the circuit and energizes the first speed solenoid. 
As the gears are engaging and while the sliding member is within 
about % inch of being at the end of its movement, the pawl G, 
see Fig. 414, falls back due to the pull of the magnet against 
the trigger N, which is attached to the switch operating pawl 







ELECTRIC GEARSHIFTS AND TRANSMISSIONS 471 


L. The pawl L, due to this action, is made to raise out of engage¬ 
ment with the stem of the master switch and the switch opens 
instantly due to the action of the spring O. The time of this opera¬ 
tion during which current is drawn from the battery is in the 
neighborhood of one-third of a second. 

Wiring of Gearshift 

A complete wiring diagram of the electric gearshift is shown 
in Fig. 417. A single wire leads from each solenoid through the 



terminal block to its particular button, while the other terminal 
of all the coils is connected to a common terminal thence to the 
master switch and battery. The remaining terminal of the bat¬ 
tery is connected to a common bus beneath the selector switches. 
The connectors at the terminal block are considerably simpli¬ 
fied by making each terminal a different size so that the wires 
can be replaced only on the terminals where they belong. 

The following are some of the most likely causes of trouble 
in the operation of the electric gearshift: 

First, exhausted or too weak a storage battery. 

Second, a break in the link connecting L to the clutch pedal. 

Third, dirt in the master switch contacts or wear of same, thus 
preventing contact. 

Fourth, failure of the spring O, which closes the master switch. 

Fifth, loose connections due to vibration at the terminal block 
or selector switches. 

Sixth, jamming of solenoid cores in the brass tubes due to 
































































472 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 
the shaft getting out of alignment. This may be tested by using 
the emergency hand lever to see if the gears shift easily. 

Seventh, broken connections in the wires or windings, which 
are not very likely to occur on account of the excellent protection. 

Woods Dual Power Car 

Motor cars propelled by a combination gasoline and electric 
powerplant are called dual power cars. The possibilities in the 
arrangement of the control of a car of this kind are very great, 
yet the control must be as simple as the ordinary gasoline car 
and at the same time allow the driver to use both the engine and 
the electric powerplant to the best advantage under all conditions 
of driving. Some of the advantages of the dual power system 
will be apparent after reading the description of the operation 
of the engine and motor combination. One of the best examples 
of a car of this type is found in the Woods dual power car, manu¬ 
factured by the Woods Motor Co., Chicago. The manufacture of 
this car has been discontinued, but a description of its operation 
will be given as it is quite interesting and instructive. 

The powerplant of the Woods dual power car, a plan view 
of which is shown in Fig. 418, consists of a four-cylinder Con¬ 
tinental 234 in. gasoline engine, a magnetic clutch of Cutler- 
Hammer make, a compound-wound dynamotor manufactured by 
the General Electric Co. and rated at 48 volts and 60 amperes 

and a special Exide storage battery of 24 cells having a capacity 

of 115 ampere-hours based on a 5-hour discharge rate. 

The engine, clutch and dynamotor are combined into a single 
unit from which the power is transmitted direct to the rear axle 
without passing through a variable gear. A Baush undermounted 
worm gear is used in the rear axle, having a reduction of 8.25 
to 1. 

The magnetic clutch is of the plate variety and is combined 
with the flywheel. A coil is set into a recess cut in the flywheel 
rim, and when this coil is energized the clutch plate is drawn 

against the flywheel rim by the magnetic force produced by the 

current. The clutch plate is faced with asbestos fabric, and the 
clutch cannot be seriously injured by slipping. 

The dynamotor is of the compound-wound type and its motor 
characteristics are somewhat different from the characteristics 
of the motors found in the ordinary electric vehicle. When the 
car is being driven by the gasoline engine alone, the clutch cur¬ 
rent is taken direct from the armature of the dynamotor. The 


ELECTRIC GEARSHIFTS AND TRANSMISSIONS 473 



Fig. 418 —Plan view of powerplant of Woods’ Dual Power motor car which is a combination gasoline and electric 











































474 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

dynamotor is used in starting the car when the engine is at rest, 
and acts as an electric motor. 

The starting controller, or the control panel as it is called, 
and the reversing switch are located under the driver’s seat and 
there is a shunt field control rheostat under this foot board. There 
are two finger levers on the steering wheel. The outer of these 
two levers controls the field rheostat, and when this lever is at 
the top of the wheel, all the field resistance is in circuit. The 
inner finger lever controls the clutch circuit and the throttle. 
When the car is standing and the engine is idle, both finger levers 
are near the bottom of the sector on the steering wheel, and mov¬ 
ing these levers forw r ard or up has the effect, while the car is in 
operation, of increasing the speed, and in this respect the control 
is similar to the gasoline car. The first slight movement of the 
inner finger lever opens the throttle of the gasoline engine, and 
continued movement of this same lever closes the circuit of the 
magnetic clutch, which operates on full battery voltage, except 
when the car is being reversed, when the clutch is free or when 
the car is being driven by the gasoline engine alone, when the 
clutch current is taken direct from the armature of the dynamo- 
tor. The throttle continues to open as the lever is moved upward 
until the top-notch position of the lever is reached. 

The main switch on the control panel, which connects the 
dynamotor to the battery, is not operated directly or mechanically 
by the driver but through the medium of a solenoid. 

In addition to the main switch for connecting the dynamotor to 
the battery, there is a secondary switch located under the main 
switch. The purpose of this secondary switch is to short-circuit 
the starting resistance when the current drawn from the battery 
by the dynamotor, which is operating as a motor, has dropped 
down to about 175 amperes. This operation of the secondary 
switch is accomplished by a differential electromagnet. The 
switch is held open by a series winding through which the main 
current of the dynamotor passes and is closed- by a shunt wind¬ 
ing. At the moment of starting from rest, the motor draws a 
very heavy current from the storage battery, which may amount 
to as much as 400 amperes. This very large current makes the 
series winding very powerful and the secondary switch is held 
in the open position, although the shunt winding tends to close 
it. As the current taken by the motor decreases in value the 


ELECTRIC GEARSHIFTS AND TRANSMISSIONS 475 


magnetic action of the shunt winding finally overpowers the 
series winding and the secondary switch closes, cutting out the 
starting resistance. 

Adjacent to the main and secondary switches is a reversing 
switch by which the armature leads of the dynamotor are re¬ 
versed to permit backing the car by electric power only. There 
is an interlocking mechanism between the right-hand control 
pedal and the reverse switch, so arranged that the reversing 
switch cannot be operated unless the right-hand control pedal 
is pressed forward until the brake is applied. A complete wiring 
diagram of the car showing all connections is given in Fig. 419. 

In starting the car the operations are as follows: First the 
lock switch on the steering wheel is turned to the “on” position, 
which closes the main switch operating solenoid at this point and 
the ignition circuit also is closed. Next the outer finger lever 
is moved a short distance up on the sector, which closes the cir¬ 
cuit of the main switch solenoid at another point. The circuit 
of the main switch solenoid is now complete and the main switch 
closes, causing the car to start forward as an ordinary electric. 
To start the engine the inner finger lever is moved up on the 
sector a short distance. The first motion of this lever opens the 
throttle slightly and further movement closes the magnetic 
clutch circuit and opens the throttle more. As the throttle is 
opened up still more the engine speeds up or tends to do so and 
tlius assists the electric motor in propelling the car. If the field 
resistance of the motor remains fixed in value and the power sup¬ 
plied by the engine is increased by opening the throttle, .then the 
speed of the car will be increased slightly and the engine will 
supply a larger and larger part of the total power supplied to 
the propeller shaft until the motor is delivering no power at all, 
as the voltage generated in its armature at this higher speed is 
then equal and opposite to the voltage of the battery. A further 
increase in speed changes the motor to a generator and it starts 
to charge the battery. The speed at which the machine changes 
from a generator to a motor or from a motor to a generator will 
depend upon the value of the resistance in the field circuit, pro¬ 
vided the battery voltage is constant. The lower this resistance 
the lower the speed at which this change takes place. Weaken¬ 
ing the field of the dynamotor lowers its voltage and decreases 
its generator action if it is acting as a generator or tends to 


476 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


































































































































































































ELECTRIC GEARSHIFTS AND TRANSMISSIONS 


477 


increase the speed if it is acting as a motor. It is possible to run 
the car on the gasoline engine alone with the dynamotor entirely 
disconnected from the battery. 

Magnetic Braking 

If the voltage in the armature of the dynamotor is greater than 
the voltage of the battery, a charging current will be sent through 
the battery and the dynamotor acts as a generator. Power, of 
course, is required to drive the armature of the dynamotor when 
it is delivering power to the battery and this power, as in the 
case of dynamic braking, may be derived from the rear axle due 
to the tendency of the car to run down hill or coast. This brak¬ 
ing effect can be increased by cutting out resistance in the field 
circuit. This results in the energy stored in the car being trans¬ 
formed into electrical energy in the battery instead of being 
wasted in heating and wearing the brake bands. 

Entz Transmission 

The principle of operation of the Entz transmission is really 
that of a slipping clutch. This transmission is an electro-magnetic 
clutch which is always slipping, sometimes a great deal, sometimes 
a very little; and the energy dissipated by the slip is recovered 
to be used again later on. If a car had a clutch made of some 
material which could not be burnt or worn out, it would be possible 
to arrange a transmisison by a purely mechanical device for 
tightening or loosening the grip of the clutch, but if this were 
done, the instant the clutch began to slip energy would be wasted 
in the form of heat. This heat energy could not be recovered, and 
also the more we wanted to use the slip so as to give the effect 
of a lowered gear ration, the greater the proportion of the energy 
that would be wasted. 

The Entz magnetic transmission is a clutch that can be tight¬ 
ened magnetically, but the slip creates electrical energy instead 
of heat energy, and this electrical energy is used to drive the car. 
The power of the engine is delivered at high speed, and relatively 
low torque, and transformed into power at low speed and high 
torque at the rear axle without any direct mechanical connection 
through gears or a slipping mechanical clutch of any kind. 

The two essential elements of the electrical transmission, that 
central station work for nearly two geenrations has proved good 


478 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 420— Cross-section oj the complete Entz magnetic transmission 























































































































































ELECTRIC GEARSHIFTS AND TRANSMISSIONS 479 


an a reliable are an electric generator and motor. Added to this is 
the extremely important point that the brushes and commutator 
bars which are the only parts of an electric generator and motor 
that are at all likely to wear out are hardly ever used anything like 
so hard as they would in lighting service. Like all other transmis¬ 
sions, the Entz transmission does most of the work on high gear, 
and the difference in the speed between the electrical moving 
parts is then only from 60 to .100 r.p.m., as compared to several 
hundreds of revolutions for a central station dynamo or several 
thousand for motor car lighting generator. It is thus obvious 
that so slow a rubbing speed of brushes on the commutator as 
this can produce but very little wear, and the life of the parts 
ought to be very good. 

General Arrangement of Parts 

Turning to Fig. 420, which is a cross-section of the complete 
transmission, it is seen that the field magnets and coils of the 
generator from the flywheel of the engine. Neglecting the motor 
part of the transmission, the armature of the generator is on a 
shaft running free from a spigot ball-bearing in the flywheel 
and attached at the other end to the driveshaft and to the bevel 
pinion of the rear axle. Thus the armature of the generator runs 
always at propeller shaft speed. 

The effect of running the engine and so spinning the field mag¬ 
nets of the generator is to produce currents in the armature which 
cause a magnetic attraction between the armature and the field. 
This is equivalent to tightening the fields upon the armature 
if we follow the clutch analogy, so the armature tries to turn 
with the field and will do so if the resistance to motion of the 
car as a whole is not too great. This means that part of the 
energy delivered by the engine is used in developing electrical 
energy in the armature and part to the direct mechanical work 
of turning the propeller shaft and so driving the car. Now this 
electrical energy which is developed in the armature of the gen¬ 
erator is taken to the second part of the transmission, which is 
an electric motor. This is also sho 1 ^ in Fig. 420, and its field 
man-nets are fixed stationary, while the armature is keyed to the 
same shaft as the armature of the generator. Thus, whatever 
else happens the two armatures are always running at the same 
speeds, and that speed is the speed of the propeller shaft. 


480 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Various Positions of Controller 

On the foot, or lower, end of the steering column is an aluminum 
box containing sundry resistance coils and several switches. The 
effect of moving the controller lever on the steering wheel is 
described in electrical terms, and the description should be read 
with continuous reference to Fig. 420, as well as the various cir- 



Fig. 421 —Controller lever on steering wheel for Entz magnetic 
transmission 


cuit diagrams given for each position of the controller, remem¬ 
bering all the while that: 

(a) The generator field runs at engine speed. 

(b) The motor field is stationary. 

(c) Both armatures move together at propeller shaft speed. 
Neutral Position—All circuits are open and no electrical energy 

is being generated or used. The battery is idle unless in use on the 
lamp circuit at night. A diagram of the connections for this 
position is given in Fig. 422. 

Cranking Position—Current from the battery is switched into 






ELECTRIC GEARSHIFTS AND TRANSMISSIONS 481 



Fig. 422 —Connections for neutral position of controller 
and electric brake 




Fig. 423 —Connections for cranking position of controller 



Fig. 424 —Connections for charging position of controller 


the generator, causing it to behave as a motor and spin the engine. 
The connections are shown in Fig. 423. 

Charging Position—When the control lever is in the charging 
position, the battery may be given a much higher rate of charge 
than would be safe to establish for running conditions. So that 




































































































































482 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


if, for any reason, the battery should be run down, it can be 
brought up in a short time, as a high rate of charge is permissible 
for a battery that has not reached the gas point and is not warm. 
The connections for this position of the controller are shown in 
Fig. 424. 

First Speed Position—Generator is producing light clutching 
effect and supplying maximum current to the motor. There is 
a maximum difference between engine and propeller shaft speeds, 
and greatest torque or pulling power is being developed. Con¬ 
nections are shown in Fig. 425. The generator field is shunted 
so as to weaken it, while the motor field is full strength, being 
unshunted. 

Second Position—Clutching effect of the generator is increased 
and the current supplied to the motor is decreased, which results 
in the car speeding up. The connections are shown in Fig. 426. 
Both the fields are unshunted, but the motor field is still the 
stronger, due to its being wound with more turns. 

Third Position—Clutching effect of the generator is increased 
further and transmits more of the driving power direct to the 
propeller shaft. The motor docs the work and the car increases 
in speed. The connections are shown in Fig. 427. The generator 
field is unshunted, but the motor field is shunted, and it is weak¬ 
ened as compared with the generator field, in which case it gives 
less torque for a given current but also less counter electromotive 
force, and therefore less slip at the generator. 

Fourth and Fifth Positions—The generator does more work 
and the motor less at the fourth position than in the third posi¬ 
tion, and there is a similar change in passing from the fourth 
to the fifth position. The generator field is unshunted but the 
motor field is shunted, and the resistance of this shunt is de¬ 
creased as the controller moves toward a higher position. 

High Speed Position—In this position the generator clutching 
effect has increased to nearly locking point, and all the driving 
power is being transmitted direct to the propeller shaft. The 
motor no longer assists the generator but itself acts as a generator 
to charge the storage battery. The connections are shown in 
Fig. 428. It will be noticed that the motor has a shunt field 
in this position of the controller, which is opposed by a series 
field in the battery circuit, making it a differential generator 
with an inherent self-regulating characteristic. 


ELECTRIC GEARSHIFTS AND TRANSMISSIONS 


483 




Fig. 425 —Connections for first-speed position of controller 



Fig. 426 —Connections for second-speed position of controller 



Fig. 427 —Connections for third-speed position of controller 





















































































































































































484 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Electric Braking 

An additional feature of the transmission is to provide an 
extremely powerful electric brake which automatically releases 
as the car slows down. It cannot be used for stopping the car 
altogether, because its breaking power depends upon the motion 
of the vehicle, but it is very effective when the car is traveling 
fast. If the controller lever be put into the neutral position 
when the car is running, the heavy current induced by the motion 
of the car in the circuit shown at the right in Fig. 422 causes a 
heavy retarding action to the progress of the car. On grades this 
electric brake will keep the speed down to 15 or 20 m.p.h. 

Merits of Entz Transmission 

Some of the merits of this transmission as pointed out by its 
manufacturers are as follows: In this system there are no auto¬ 
matic cutouts or regulators or roller ratchets. There are no 



Fig. 428 —Connections for sixth-speed position of controller 


chains or gear drives for any of the parts. There are two ample 
sized electric machines, direct connected, and a drum controller. 
These take the place of separate starting and lighting systems 
with their complicated means of driving and regulation, of the 
friction clutch and its actuating mechanism, and the gearshifting 
transmission, as well as such telescopic and universal joints and 
numerous grease cups that attend them. The car can be brought 
up to speed without a jar or jerk. All power impulses of gasoline 
engine are practically eliminated, and the torque delivered by 
the propeller shaft to the rear axle is very uniform. The speed 
of the car is easily managed in traffic and on grades without the 
necessity of shifting gears. 





























































CHAPTER XXVIII 

Reading Wiring Diagrams 

INDIVIDUAL systems of starting, lighting and ignition for 
* motor cars as manufactured by the various companies vary 
considerably in detail, and the component parts of the same 
type and make of system are often of different construction when 
used on cars of different make, but in principle all are alike. 

Every standard starting, lighting and ignition system must 
include the four following important component parts: 

1— The generator. 

2— The storage battery. 

3— The electric motor. 

4— A means of producing the spark in the engine cylinders. 

The function of these component parts are: 

The generator is connected mechanically to the engine and 
when its armature is made to rotate by the engine, a part of 
the mechanical energy of the engine, or its ability to do work, is 
transformed into electrical energy and the electrical energy 
which is delivered by the generator may be used in charging the 
storage battery, in lighting the lamps, operating an electric 
heater, producing the spark in the engine cylinders, etc. 

The storage battery serves as a means of storing energy while 
it is available from the generator and then delivering it at such 
time as it may be called upon to do so. Thus, while the engine 
is operating the generator and the generator is capable of de¬ 
livering electrical energy, this energy may be stored in the bat¬ 
tery and then delivered to the starting motor, lights, ignition 
system, etc., as conditions may demand. 

The electric motor is a device for transforming electrical 
energy into mechanical energy which may be used in cranking 
the engine. The electrical energy supplied by the storage bat¬ 
tery when it is allowed to discharge through the starting motor 
circuit thus is utilized in starting the engine. 


86 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The ignition device transforms electrical energy, which may 
be supplied by the storage battery, dry battery or magneto, into 
heat energy in the spark in the engine cylinders and thus pro¬ 
duce the explosion of the gases and cause the engine to operate. 

In addition to the four component parts given, various addi¬ 
tional parts, such as wires, switches, connectors, ammeters, volt¬ 
meters, fuses, circuit-breakers, automatic current and voltage 
regulators, etc., are necessary for the convenient and safe opera¬ 
tion of the four main component parts. 


Wiring Diagrams and Symbols 

All manufacturers of electrical equipment supply wiring dia¬ 
grams which show the proper connections of their apparatus. 
Such wiring diagrams often permit a circuit to be traced much 
more easily than is possible if the actual wires on the car have to 
be followed through. Consequently the ability to read a wiring 
diagram is essential in locating troubles in circuits. 

Certain conventional symbols have come to be used almost uni¬ 
versally in wiring diagrams to represent the different pieces of 
apparatus and their connections. These are shorthand pictures 
of the thing represented. They are not all standard, but some of 
them, such as the symbols for the ground connection and the bat¬ 
tery, are standard. Lamps, for instance, may be represented by 
a circle, a bulb, or the complete lamp assembly. 

The more usual symbols are illustrated on the facing page. 


A Typical Installation 

Before taking up the individual systems we will take up an 
assumed system which is typical of all the common installations 
on modern cars. In this, illustrated in Figs. 1, 2 and 3, the side¬ 
lights are incorporated with the headlights, there being two 
bulbs in each headlight, one low candlepower and one high 
candlepower. Lights and horn are connected through a main 
switch on the cowl. 

Some means of connecting and disconnecting the generator 
and battery is provided in the majority of cases to prevent a 
discharge of the batteries through the generator when the volt¬ 
age of the generator is lower than the voltage of the battery. 


READING WIRING DIAGRAMS 


487 


Conventional Wiring Symbols 



Positive. 


Negative. 



Battery, either storage or dry cells. 



Generator, Commutator and Brushes. 




The proper method of showing a coil which surrounds an iron 
core but very seldom used on Delco Drawings. 


MUh 

-W- 


The method used in showing a coil where there is no chance 
of confusion—Used in field coils, ignition coils, etc. 

The method used to show resistance such as a resistance unit 
and charging resistances. 




-i 

0 . 


Contact points such as in switches, distributors, etc. 

Ground connection where the wire is connected to the chassis, 
engine or generator. 

Method used to show lighting switches. 

Motor Commutator and brushes with brush lifting switch. 


-ilWWM 

-mm-I 


Primary and secondary windings of an ignition coil. 



"T“ 


.Condenser. 

Crossed wires not connected. 

A round dot on a circuit diagram usually represents a termi¬ 
nal for connecting a wire or wires. 







488 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



l ±£±±£ 2 . _I 

Fig. 1 —Mechanical and electrical connections of a typical tliree-unit single-wire starting, lighting and ignition sys¬ 
tem. In Fig . 2 the actual location of these units and course of the wires are shown. In Fig. 3 the wiring dia¬ 
gram of this system is illustrated 




















































































































































READING WIRING DIAGRAMS 


489 

This device is called a cut-out and it has been omitted from the 
diagrams, for the sake of clearness. 

Tracing the Circuit 

The generator in this case is connected to the engine shaft by 
a silent chain, and the circuit through which the generator sends 
the charging current for the storage battery may be traced in 
Figs. 1, 2 or 3 as follows: Starting with the ground connection 
Gl, you follow along the wire 1, through the generator along wire 
2, through the ammeter, along wire 6 to junction point 7, then 
along wire 8 to the battery, through the battery and along wire 
9 to the frame of the car, which is the same as the ground con¬ 
nection Gl, from which you started, since all indicated ground 
connections are in reality connections to the frame, and in such 
cases the electrical circuit is completed through the chassis. 

It sometimes is difficult to determine from a wiring diagram 
or from the wires themselves on a ear just which of two or more 
wires at a junction are taking the current. This always can be 
ascertained by remembering that current will flow only where 
there is a complete circuit, for instance, in the circuit just men¬ 
tioned all the switches are open, except the connection between 
the generator and battery, and that therefore is the only com¬ 
plete circuit. Consequently when we come to the junction of the 
two wires at the ammeter we know that no current is going up 
on wire 4 to terminal 26 on the cowl switch because this switch 
is open, and the horn button and the cowl light switch 33 are open 
so that there is no connection to any circuits out of the switch. 
Likewise when we come to junction point 7 we know that all the 
current must pass down through wire 8, and none through wire 
12, because the starting switch is open. 

The ignition in this case is provided by a high-tension mag¬ 
neto driven from the engine shaft by gears. The ignition cir¬ 
cuit is not shown in detail but it is controlled by the ignition 
switch shown in the upper right-hand corner. 

The motor circuit may be traced in a similar manner by start¬ 
ing with the ground connection G2. You follow along the wire 
10, through the motor along the wire 11 to the starting switch, 
through the starting switch, when it is closed, along the wire 12 
to the junction point 7, along the wire 8, through the battery, 
along the wire 9 to the frame of the car, which is the same as 
the ground connection G2, from which you started. The motor 


490 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

switch in this case is operated by pressing on a pedal, which 
also causes a pinion P on the motor shaft connection to engage 
with a gear on the flywheel and thus establish a mechanical 
connection between the motor and the engine shaft. This me¬ 
chanical connection between the engine and the motor is main¬ 
tained and the electrical circuit through the motor and battery 
remains closed as long as the pedal is pressed down. 

The electrical circuit for the low-candlepower headlights, 
when they are operating off the storage batteries, may be traced 
as follows: Starting with the frame of the car or grounded 
terminal of the battery you pass along wire 9, through the bat¬ 
tery and along wire 8 to junction point 7, then along wire 6 
through the ammeter along wire 4 to terminal 26 of the cowl 
switch, then from terminal 14, when the switch is closed, along 
wire 15 through fuse 16, along wire 17 to the junction point 18, 
where the circuit divides, part of the current passing through 
bulb LI to ground G3 and part through bulb L2 to ground G4. 
The ground connections G3 and G4 are the same as the point 
from which you started. The circuit for the high-candlepower 
headlight is the same as that for low-candlepower lights up to 
terminal 26, then with switch thrown to terminal 23 you pass 
along wire 22, through 21, along wire 20 to junction point 19, 
where circuit divides, part of current going through bulb L3 
to ground G5 and part through L4 to ground G6. It will be ob¬ 
served that this last circuit was traced through the battery in 
the opposite direction to that of the generator and motor cir¬ 
cuits, but the results are just the same except in one case you 
will follow along the circuit in the direction of the current and 
in the other case in the opposite direction. In each case you 
must return to the point from which you started. 

The circuit for the cowl light is the same as the headlights up 
to switch terminal 26, then along wire 24 through the cowl light 
switch 33 and bulb along wire 25 to the ground connection G7. 
The circuit for the horn is the same as that for the headlights 
up to terminal 26 on the cowl switch, then along wire 27 through 
fuse 28, along wire 29 and /through the horn along wire 30 
through the horn button when it is closed to the ground con¬ 
nection G8. 

The circuit for the tail light may be traced as follows: From 
the frame of the car along wire 9 through the battery along 
wire 8 to the junction point 7 along wire 6 through the ammeter 


READING WIRING DIAGRAMS 


491 


along wire 4 to terminal 26 to terminal 13 when switch is closed 
through wire 3 through the fuse 31 along wire 32 through the 
taillight and to the ground connection G9. 

Assuming the generator is not charging the battery and that 
all lights are turned on and the horn button is closed, determine 
the current in the different wires. Wires 9, 8 and 6 will be car¬ 
rying the total current supplied by the battery. The current in 
wire 12 will be zero, since the motor switch is open, so that the 
current through the ammeter is that taken by the large and 
small headlights, horn, taillight and cowl light. Wires 4, 3 and 
32 carry the current for the taillight. Wire 4 carries the cur¬ 
rent taken by the horn, headlight, taillight and cowl light. 
Wires 27, 29 and 30 carry the current taken by the horn. Wires 
15 and 17 carry the current taken by the low-candlepower head¬ 
lights. Wires 20 and 22 carry the current taken by the high- 
candlepower headlights. If the motor switch is closed, the cur¬ 
rent in wires 8 and 9 will be equal to the current supplied by 
the battery, and wires 10, 11 and 12 will carry the motor current. 

Assuming the motor circuit open and all the other circuits 
closed and the generator delivering current, if the current de¬ 
livered by the generator is just equal to the current taken by the 
born, taillight, cowl light and headlights, there will be no cur¬ 
rent in the ammeter. If the current delivered by the generator 
exceeds in value the current taken by the horn, tail, cowl and 
headlights, the current in the ammeter will be toward junction 
point 7, and the ammeter will show charge. Should the value 
of the generator current exceed that of the combined currents 
taken by the horn, taillight, cowl light and headlights, a charg¬ 
ing current will be sent along wires 6, 8 and 9. When all the 
lamps and horn are disconnected, all current supplied by the 
generator passes through the battery. If the terminal voltage 
of the generator is lower than the terminal voltage of the bat¬ 
tery, then the battery will supply current to all the lamps and 
horn and in addition send a current through the generator, un¬ 
less the connection between the generator and battery is broken 
by some form of cut-out, and the generator will tend to operate 
as a motor. When the batt«ry is supplying current through the 
lights or horn the ammeter will show discharge. 

The reader must bear in mind always that every electrical 
circuit is just like a circle. It has neither beginning nor end. 
It is absolutely imperative that you be able to trace the various 


492 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


































READING WIRING DIAGRAMS 


493 


electrical circuits on the motor car to clearly understand their 
operation and know how to test and locate readily the various 
causes of trouble which are likely to arise. Always bear in 
mind that electricity is not used up and just as much returns 
to the generator or battery as leaves it. It is the energy, or 
ability to do work, possessed by the electricity when it leaves 
the generator or battery when the battery is discharging which 
is used in the electrical circuit. 

Using a Wiring Diagram 

The primary purpose of every wiring diagram of a starting, 
lighting or ignition system is to show the proper electrical 
connections between the various devices which go to make up 
the complete systems. These wiring diagrams are often quite 
a puzzle to the inexperienced man, and also to the man who has 
not taken time to give these the necessary consideration in con¬ 
nection with the installation, maintenance or repair of the dif¬ 
ferent systems which he has worked upon. 

One of the chief reasons why a wiring diagram is of no real 
assistance to the majority of men working on the electrical 
equipment of motor cars is due to their lack of a clear conception 
of the proper operation of the various electrical circuits which 
go to make up the complete systems. Another, and almost 
equally important reason, is the lack of sufficient imagination 
to follow along the various electrical circuits just as though 
the wires and different devices were suspended in space and 
absolutely independent of all other parts of the car. The rela¬ 
tions of the component parts of a starting, lighting and ignition 
system were shown in Fig. 1. The various electrical circuits 
were traced in detail for practically all conditions of operation 
of the different combinations. 

The actual locations of the different parts of a starting, light¬ 
ing and ignition system similar to the one shown in Fig. 1 
as they would appear on the car are shown in Fig. 2, which 
might De called a ghost view of the electrical equipment and 
circuits. The various electrical circuits traced in Fig. 1 easily 
may be traced in Fig. 2 by using exactly the same descrip¬ 
tion as the same lettering has been used in both cases. 
Such a diagram should be of great value to the repair man in 
tracing the actual electrical circuits on the car, as he, by ref¬ 
erence to this kind of a diagram, easily can identify each in- 


494 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

























































READING WIRING DIAGRAMS 


495 


dividual conductor, the circuit to which it belongs and the cur¬ 
rent it is supposed to carry under normal conditions. Diagrams 
of this kind will be given in connection with the leading makes 
of systems to be described later. 

A type of wiring diagram usually supplied by the manufac¬ 
turers of starting, lighting and ignition equipment is shown in 
Fig. 3. This is a diagram of .the same system shown in Figs. 
1 and 2, and the same lettering has been used in designat¬ 
ing the different parts, wires and connections as was used in 
Figs. 1 and 2. It thus is seen that the wiring diagram itself 
merely gives the different electrical connections without refer¬ 
ence to the relative location of the different parts and devices 
forming the various electrical circuits. 

Analysis of Trouble 

The various kinds of individual troubles which may occur on 
any particular system are so numerous that it would be im¬ 
possible to expect the reader to wade through a detailed descrip¬ 
tion of each and every one. A description of the more im¬ 
portant ones and those that are most likely to occur will be 
given, and with these as a basis the reader may go on and study 
the more uncommon cases and perhaps more complicated cases. 

You must have in mind that there are three things associated 
with every electrical circuit, namely, the resistance of the 
circuit which opposes the free movement of the electricity 
around the circuit, the electrical pressure, or electricity moving 
force which causes the electricity to move through the circuit, 
and the electric current which is a measure of the rate at, which 
the electricity is moving just as the current in a river is a 
measure of the rate at which the water is moving down the 
river. The rate at which the electricity moves, or the current, 
in amperes is equal to the effective electrical pressure in volts 
acting in the circuit divided by the resistance of the circuit 
in ohms. Thus if a lamp circuit has a resistance of 2 ohms and 
the electrical pressure in this circuit is 6 volts, a current equal 
to 6 divided by 2, or 3 amperes, will be produced when the cir¬ 
cuit is closed. The effective pressure as used means the dif¬ 
ference in the sum of the pressure acting in one direction around 
the electrical circuit and the sum of the pressures acting in 
the opposite direction. Thus if a generator having a terminal 
pressure of 7.5 volts is charging a battery whose terminal pres- 


496 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

sure is 7 volts, an effective pressure of 7.5 minus 7 or .5 volts 
will be acting in the circuit. 

In order that there be an electrical current in any circuit an 
effective pressure must be acting in the circuit and the circuit 
must be closed. So in any electrical circuit in which there is 
no current the difficulty is due to there being no electrical 
pressure in the circuit or the circuit is not closed. For example, 
if the ammeter indicates zero current when the headlights are 
turned on, see Figs. 2 and 3, you immediately know the 
difficulty. Either there is no electrical pressure or the circuit 
is open. If at the same time the cowl and taillights operate 
normally, you immediately know that the difficulty is not due 
to a lack of electrioal pressure but to an open circuit. An 
inspection of the diagrams in Figs. 2 and 3 will show that 
all the various light circuits have certain wires and connections 
in common. That is, starting with the frame of the car, you can 
pass along wire 9, through the battery along wire 8 to the 
junction point 7, along wire 6 and through the ammeter along 
wire 4 to terminal 26 on the cowl switch, where the circuit 
branches to the horn, the cowl light and the tail and headlights 
through the cowl switch. If the cowl and taillights operate, 
all connections and wires along the circuit just traced are 0. K. 
up to the terminal 26 on the cowl switch. If neither the low- 
nor high-candlepower bulbs will burn, the difficulty is more than 
likely in the switch, although both fuses 21 and 16 may be burnt 
out. The fuses may be tested by connecting the terminals 
with a pair of pliers or a short piece of wire, thus closing the 
circuit if the fuse is burnt out. The connections in the switch 
may be tested by connecting terminals 26 with terminals 23 
and 19 respectively. 

If neither of these tests locate the difficulty, the circuit is 
open at some other point or it may be open at both the fuses 
and switch, in which case neither of the tests would locate the 
trouble. A test lamp whose voltage corresponds to that of 
the headlights may be used as follows in locating the difficulty. 
Mount the lamp in a socket provided with flexible terminals 
several feet long and connect one of the free ends of the flex¬ 
ible wire to the frame of the car and the other to terminal 26 
on the cowl switch. If the test lamp lights it is 0. K. and the 
circuit is, of course, O. K. up to the terminal 26, as the cowl 
light burned. Turn the cowl switch so the high-candlepower 


READING WIRING DIAGRAMS 


497 


Hght should burn and then connect the free terminal of the test 
lamp to the terminal 19, and if the test lamp burns the switch 
is O. K. If the lamp does not burn, the connection in the 
switch is at fault. If the switch is O. K., proceed to the right- 
hand terminal of fuse 21 and again test. If the test lamp burns, 
wire 22 is O. K. Then touch the left-hand terminal of fuse 21, 
and if the lamp burns the fuse is O. K. Next go to junction 
point 19, if it is possible to make electrical connections there; 
if not, open up headlights and test circuits by applying end 
of test circuit to terminals in lamp sockets. Proceed along 
the circuit in this manner until you reach a point on the circuit 
• where the test lamp does not light. The circuit is open between 
this point and the last point where it did light. This same 
line of reasoning will apply to every electrical circuit on the 
car, and difficulties caused by open circuits easily may be located 
by following carefully the wiring diagram. 

The importance of the wiring diagram in locating cases of 
trouble thus is readily seen, and you cannot become too familiar 
with these diagrams for the • different systems. 

If the system happens to be grounded at some point that is 
not supposed to be grounded you can test for such a ground 
as follows. First remove all grounds from the system as shown 
in the wiring diagram. This may be done by disconnecting 
the grounded terminals of the battery and the grounded ter¬ 
minal of the generator and removing all lamps. The ground 
connection for the horn circuit and starting motor circuit should 
not interfere with any test on these two circuits, which are open 
at the horn button and starting switch respectively. Now 
connect the terminal of the battery, which normally is grounded 
to the frame of the car by the test lamp circuit. If the wiring 
to which the other terminal of the battery is connected hap¬ 
pens to be grounded, the lamp will light, provided the resistance 
of the ground connection is not too high. The different light cir¬ 
cuits then may be tested by disconnecting them in turn from the 
battery by taking out the fuses or loosening the wires from under 
the screw terminals if no fuses are in the circuit. 


CHAPTER XXIX 


Maintenance and Repair of Electrical 
Equipment and How to Diagnose 
Electrical Troubles 

PART I 

Points on Maintenance and Repair 

E LECTRICAL troubles may be divided roughly into three 
classes, namely, troubles due to wear of so-called wearing 
parts, derangement of the wiring and connections and internal 
electrical defects. Of these the average garage repairshop should 
be equipped to handle the first two, while the last mentioned class 
should be taken care of in electrical service stations or repair- 
shops. To do the ordinary electrical repair work remarkably lit¬ 
tle equipment is needed beyond that found in every machine shop. 

Soldering Joints in Wiring 

A good part of all electric work consists in making soldered 
joints, and a soldering outfit is a first requisite. This consists of a 
soldering iron, Fig. 331, or, preferably, several soldering irons of 
different size, a supply of solder in wire form and soldering fluid 
or flux. In most of the work the ordinary soldering flux, consist¬ 
ing of a solution of zinc chloride, can be used, but where a high 
degree of insulation is required and where soldered joints have to 
be made to parts of different electrical pressure that are sepa¬ 
rated only by thin strips of insulating material, a non-acid flux, 
of which there are several on the market, sometimes is used. 
Rosin will serve the purpose. None of these special fluxes make 
the solder run as freely as the regular flux, as they do not dis¬ 
solve the layer of metallic oxide on the surfaces to be soldered as 
quickly. The ordinary soldering flux usually is purchased in the 
form of a salt, and the fluid flux is made up as required. 


MAINTENANCE AND REPAIR 


499 


When making a soldered joint between two wires, the insulation 
is pared off for a certain length, the wires are cleaned mechanically 
by sandpaper or emery cloth, twisted together, daubed with solder¬ 
ing flux by a stick or swab and soldered. In making joints be¬ 
tween wires insulated with cotton or silk, commonly known as 
magnet wires, it is not necessary mechanically to clean off the 



Fig. 331 —Soldering iron 



END/ OF WIRE/ PARED AND CLEANED 



Fig. 332 —Various steps in making a wire joint 


ends of the wire, which is comparatively clean when the insula¬ 
tion is stripped off. But rubber or composition-covered wire should 
be scraped or rubbed off. The steps are shown in Fig. 332. 

Soldered and similar joints are insulated by adhesive or fric¬ 
tion tape, which comes in rolls. This is wrapped around the wire 
in helix fashion, with successive turns overlapping. The tape is 
wrapped over a sufficient length of the wire at the joint to extend 




















500 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

a short distance over the insulation on both sides of it. The 
warp of the tape fabric runs parallel with the tape, and the latter 
can be torn readily into two or even more strips if the size of the 
joint permits of more neatly wrapping the narrow strip than the 
full width of the tape. Owing to the adhesive quality of the 
tape, the end need not be especially fastened. 

A connection between a wire and a stationary part never should 
be made by wrapping the bared wire around a screw or binding 
post and screwing a nut down upon it. Such a joint does not 
furnish a good connection. Besides the -wire will break off after 
having been fastened and loosened a few times. Connectors 
should be soldered to the ends of the wires and drilled to pass 
easily over the binding posts. Such joints can be broken and re- 



Fig. 333 —Methods of connecting to terminal posts, ground, etc. 


made any number of times without trouble, and, besides, they give 
a large effective contact area. See Fig. 333. 

To insure the durability of the wiring no part of it must be 
subject to vibration. This is fully cared for in most modern ma¬ 
chines, in which the wires are run through flexible metal conduits. 
When this is not used, it is well to fasten the wire down by cleats 
in a substantial manner. Also, in replacing parts of the wiring 
system wires of substantially the same size as the original one 
should be used. No. 14 B & S gage is used largely for lighting and 
charging circuits and No. 00 for starter connections. 

In a ground return single-wire system there are many ground 
connections, and these are likely to give some trouble. The num¬ 
ber of connections is no greater than in any insulated return wir¬ 
ing system, but in the latter case the conducting surfaces at the 


« 


























MAINTENANCE AND REPAIR 


501 


joint are usually both of non-corrosive metals, whereas the ground 
connections generally have to be made to parts subject to rust. 
An especially good ground connection has to be made in the start¬ 
ing motor circuit, as this has to carry a very heavy current, and a 
poor contact would greatly cut down the power and cranking 
speed of the starting motor. Therefore, if a starting motor seems 
to be not quite up to power, after having made sure by an hydrom¬ 
eter test the battery contains sufficient charge, the contacts and 
joints in the starter circuit should be examined, particularly the 
starter switch contacts and the ground connection joints. To 
secure the good electrical contact necessary for the starter ground 
connection, a brass plate often is riveted to the frame, and the 
connector lug on the ground wire is bolted to this plate. Besides 
being riveted the brass plate may be soldered to the frame, so 
rust or dirt cannot impair the contacts. 

Care of Generators and Starting Motors 

Charging generators and starting motors are virtually the 
same type of machine and subject to th3 same troubles. The 
bearings of both, of course, require oiling occasionally, but as 
these machines mostly are fitted with anti-friction bearings, only 
a small amount of oil is required, and no serious trouble is likely 
to result from lack of lubrication, as the only object of the lubri¬ 
cant in ball and roller bearings is to prevent rusting of the parts. 

It has been a mootable question as to whether commutators 
should be lubricated. Some makers advise strongly against any 
lubrication, on the ground that excessive lubrication, which is 
always possible if an unskilled or careless person looks after the 
machine, gives rise to no end of trouble. The carbon brushes, as 
well as the commutator copper bars, wear away in service, and 
metal and carbon dust, which conducts electricity, accumulates 
within the generator or motor. If the interior of the machine is 
kept dry, this dust can be blown out at intervals, but if there is 
an excess of oil in the machine the dust will cake on the various 
parts, forming short-circuits, grounds, etc. On the other hand, 
it cannot be denied that a thin film of oil on the commutator will 
cut down the brush friction and reduce not only the heating of 
the commutator and loss of energy but also the wear of tho com¬ 
mutator and brushes. The best way to apply the oil to the com¬ 
mutator, and at the same time make sure that there will be no 


502 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


excess of it, is to dip the finger slightly into the oil and then hold 
it to the commutator as the latter revolves. 



Of the wearing parts of generators and motors those that re¬ 
quire the most attention are undoubtedly the brushes. These must 
slide freely in the brush holders and yet must make good elec¬ 
trical contact with them. 
Where very heavy currents 
have to be carried, as in 
starting motors, some makers 
— p £R consider it inexpedient to de¬ 
pend on the frictional con¬ 
tact between the brush and 
the holder to conduct the 
current, and short flexible 
cables, known as pigtails, 
whose ends are fastened to 
the brushes and the holders 
respectively, are provided. 
In order that the electrical 
resistance between the 
brushes and the commutator 
may not be too great, the 
brushes must be pressed 
firmly against the commuta¬ 
tor, and this is the object of 
the brush springs. With 
many designs of brush hold¬ 
ers the pressure of the 

Fig. 334-Bedding a new Irush to the 8 P rln S s varies as the brushes 
commutator wear down, and, therefore, 

when. the brushes become 
too short they should be replaced. New brushes must be fitted 
or bedded to the commutator. To this end a strip of sandpaper 
is placed over the commutator under one set of brushes, with the 
paper toward the commutator. Then, while one man presses the 
brushes down, another draws the sandpaper back and forth over 
the surface of the commutator, thus wearing the contact sur¬ 
face of the brushes down until it nicely fits the contour of the 
commutator. See Fig. 334. 

Another wearing part of electric machines is the commutator. 





MAINTENANCE AND REPAIR 


503 


This generally is built up of standard copper segments with 
strips of mica between for insulation. After the surface on which 
the brushes bear has become rough, it is impossible to secure good 
electrical contact, and the commutator then must be turned down 
in a lathe. This job can be done in any ordinary repairshop. The 
armature is removed from the machine and swung between cen¬ 
ters in the lathe, and cuts are taken over the whole width of the 
bearing surface of the commutator until it is absolutely cylin¬ 
drical, that is, until all signs of the old bearing surface have 
disappeared. At the inner end of the bearing surface, just in 
front of the commutator lugs, a shallow groove generally is cut, 
Fig. 335, the idea being that at least one of the brushes shall 
extend over the edge of this groove, thus preventing the wearing 
of a ridge on the bearing surface of the commutator. 

The armature always has a slight amount of end play in its 



Fig. 335 —Groove at inner edge of the commutator 


bearing, and if a ridge were allowed to form on the surface of 
the commutator, as the armature played back and forth in the 
direction of the shaft axis, the brush would clinch the ridge and 
thus partly break contact with the commutator, causing spark¬ 
ing. After the commutator has been turned down a couple of 
times, the bars or sectors become very thin, and it then becomes 
necessary to refill it. This involves the unsoldering of all the 

































































504 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

armature wires, called leads, from the commutator lugs and the 
removal of the commutator from the armature shaft. 

The actual refilling of the commutator probably is best left to 
the maker’s service station, as it would involve too much trou¬ 
ble for the repairman to get hard copper segments of the proper 
size, as well as sheet mica properly cut, besides making a special 
clamp for assembling the bars. Instead of refilling the old com¬ 
mutator sleeve a new commutator may be fitted. These come 
with the lugs already slotted for the leads, and all that has to 
be done after the commutator is fitted to the shaft is to solder 
the leads into the slots and possibly to put on a band. In soldering 
care must be taken not to produce a short-circuit between adja¬ 
cent bars, or segments. 

Sometimes it will happen that the mica plates between adja¬ 
cent commutator segments project slightly above the surface of 
the commutator and prevent intimate contact between brushes 
and commutator segments. Mica is exceedingly hard and wears 
less rapidly than copper. The result is destructive sparking at 
the brushes. To obviate such trouble the mica may be undercut 
slightly below the surface of the commutator. 

One of the causes of a generator failing to pick up is an open 
field circuit. * After a thorough inspection of the brushes and when 
application of pressure to them has failed to remedy the trou¬ 
ble, the field circuit should be investigated. All generators of 
motor car electric systems, except those in which the field is pro¬ 
duced by permanent magnets, have shunt field windings, and the 
break may be either in the windings at their connections to the 
generator terminals or in the regulating resistances sometimes 
connected in series with the shunt field coil. A test for con¬ 
tinuity of the field circuit can be made by removing one set of 
commutator brushes and also disconnecting the battery cutout. 
Then the test points applied to the generator terminals should 
show a complete circuit through the field. 

Regulating Generator Output 

Some equipments are furnished with means for regulating the 
rate of charge, and this must be considered a very useful feature. 
Of some other adjustable motor car parts it is said that they are 
set at the factory and should never be disturbed, but this does 
not always apply to the charge-regulating device. Some opera- 


MAINTENANCE AND REPAIR 


505 


tors drive under such conditions that very little current is used for 
starting and lighting but the battery is being charged nearly all 
the time the car is on the road. In this case there is naturally a 
tendency to overcharging. Overcharging results in a constant 
loss of energy, in the production of corrosive fumes from the bat¬ 
tery electrolyte and deterioration of the battery. Other opera¬ 
tors, who do much city driving at night, use a great deal of cur¬ 
rent for starting and lighting, and owing to legal and traffic 
conditions seldom can drive at a speed where the generator is 
sending its full charging current into the battery. In their case, 
therefore, a tendency to undercharging, is a much more serious 
matter than overcharging and also much more common. 

An undercharged battery gives a dim light, is incapable of 
cranking the engine and deteriorates rapidly. Therefore, it is es¬ 
sential that the rate of charge be regulated to suit the conditions 
of operation. The most suitable rate of charge varies even with 
the seasons, as in summer less current is required both for lighting 
and starting, for lighting because of the relatively much longer 
period of daylight and for starting because during the warm 
season an engine cranks easier and picks up its cycle quicker 
than in extreme cold. 

Part II. Testing Equipment 

The sudden advent of electrical equipment other than that 
required for engine ignition, some four to five years ago, con¬ 
fronted motor car repairmen with problems quite new to them. 
Of course, there had been a certain amount of electrical equip¬ 
ment on motor cars from the very beginning, but there is lit¬ 
tle comparison between the simple ignition system, especially 
the high-tension magneto system, with its minimum of exposed 
wiring, and the rather complicated system of wiring for a com¬ 
plete set of electric lamps, electric horn, starting motor, electric 
ignition and a self-contained electric generating system. The 
puzzling nature of many electrical troubles was foreseen by some 
of the pioneers of the industry, and its realization gave rise to 
the argument against electric ignition, voiced by Levassor among 
others, that on a gasoline motor car, everything—including igni¬ 
tion —should be accomplished by gasoline. Levassor and fol¬ 
lowers, however, proved to be wrong in this contention, as elec¬ 
tricity has not only won a complete victory in the ignition field 
but also has found several other important applications. 

In the case of electrical troubles the main thing is a quick 
and correct diagnosis. The trouble may be in any of the major 


506 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

parts of the system or it may be in the wiring. The nature of the 
trouble often partly locates it, at least approximately. For in¬ 
stance, if a single lamp will not burn, the trouble.must be either 
in the bulb, socket or wiring of that lamp. It cannot be in the 
battery, the generator or the appurtenances of the generating 
system, because any fault in these parts would affect all the 
lamps alike. Similarly, if the starting motor refuses to crank 
the engine, the trouble—if the engine can be turned by hand— 
may be in the starter, its wiring, the switch, the battery or the 



</ 

Fig. 337 —Battery 
hydrometer 



Fig. 338 —Arrangement of testing lamp 


generating system of the lamps burn properly, the trouble is 
not with the battery or generating system, and this test, there¬ 
fore, limits the necessary search to the starter, the switch and 
the wiring. 

To properly diagnose electrical troubles, it is necessary to 
have a certain number of testing instruments. For battery tests 
the most important is the battery hydrometer, Fig. 337. For 
convenience in battery testing, the hydrometer generally is placed 
inside a syringe or siphon by which a certain amount of electro- 





























MAINTENANCE AND REPAIR 


507 


lyte can be withdrawn quickly from each cell of the battery and 
as quickly restored. The syringe consists of a substantially 
cylindrical glass vessel with a spout at the bottom for insertion 
into the battery filling hole and a rubber bulb at the top. By 
compressing this bulb, then inserting the spout into the battery 
cell below the level of the electrolyte and then releasing the bulb, 
sufficient electrolyte can be drawn into the syringe to float the 
hydrometer. The latter is an instrument for determining the 
specific gravity of a liquid. It is based on the physical law that 
a floating body displaces as much liquid as is equal to its own 
weight. As the hydrometer has a definite weight, if the liquid 
in which it is immersed is relatively light, it will sink into it to 
a greater depth, thus displacing a greater volume of it than if 
the liquid is relatively heavy. 

The stem of the hydrometer is graduated to show the specific 
gravity of the liquid in which it is immersed, at the level of the 
liquid. Pure water has a specific gravity of 1.000 and pure 
sulphuric acid has a specific gravity of about 1.85. The extreme 
range of specific gravity of storage battery electrolyte is about 
1.100 to 1.300. As the charge in the battery increases during 
the process of charging, the density of the electrolyte increases, 
and vice versa, as the charge decreases during the process of 
discharge, the density of the electrolyte decreases. At full charge 
the density of the electrolyte is about 1.280, and when a battery 
is completely discharged, the density is about 1.120. When the 
density is midway between these figures, the battery contains a 
half charge. 

The simplest indication of a current flowing in a circuit is a 
spark obtained on breaking the circuit at any point. A storage 
battery has little internal resistance and the current from it 
usually is sufficiently intense to give a clearly visible spark when 
the circuit is broken. This method can be applied in various ways 
to determine whether or not a circuit is faulty. 

Ammeter and Voltmeter 

An ammeter and a voltmeter are handy instruments for trac¬ 
ing electrical troubles. Reasonably accurate instruments can be 
purchased now at comparatively low prices and in the hands of 
a man with some electrical knowledge are a great help. For 
instance, with every system of electrical equipment the charging 


508 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

current at certain engine speeds should have a certain value. 
Therefore, an ammeter test of the charging current at a given 
engine speed would show whether or not an electric charging 
system is operating as it should. 

It may here be explained that an ammeter, or ampere-meter, 
shows the quantity of current in amperes flowing in a circuit, 
while a voltmeter shows the electrical pressure between the points 
to which the. voltmeter is connected. An ammeter is perhaps of 
wider use in diagnosing troubles than a voltmeter. To be able to 
properly use these instruments, the operator has to be familiar 
with their method of connection. To measure the current flowing 
in any circuit, the circuit is opened at any point and the ammeter 



is inserted at the break. On the other hand, if it is desired to 
deter ge the voltage active in the circuit, the voltmeter must 
be connected differently. The highest measurable voltage in a 
circuit is at the terminals of the current source, such as the 
battery. Therefore, to measure the voltage of the battery, the 
two binding posts of the voltmeter are connected to the two 
terminals of the battery respectively. Some voltmeters and am¬ 
meters are polarized, that is, they have their binding posts marked 
plus and minus respectively, and these binding posts must be 
connected to the corresponding sides of the circuit. With other 
types of instruments, it does not matter which way they are 
connected in circuit. 

For determining and locating troubles in the wiring and parts 
of electric systems, use is made of one or the other of a variety 
























MAINTENANCE AND REPAIR 


509 


of devices giving either a visible or an audible signal when a 
current flows through them. These include incandescent lamp 
bulbs, bells, buzzers and telephone receivers. The bulbs may 
be of the regular house lighting variety, 110-volts, and current 
from the service mains may be used. In that case it is prefer¬ 
able to use carbon filament bulbs, as these will withstand more 
vibration than tungsten filament bulbs, and though they take 
more current, this is of no consequence because the current used 
for testing is insignificant in any case. 

The testing lamp is arranged as illustrated in Fig. 338. One 
of the two strands of the cord leading to the lamp is cut, usually 
close to the lamp, and to each end thus obtained is soldered a 
length of lamp cord 4 to 6 ft. long, the soldered joints being 
carefully taped with adhesive tape as used by electricians, to 
prevent them from coming in metallic contact. The other ends 
of these two wires are wrapped around and soldered to steel rods 
or spikes about 6 in. long, whose free ends are ground to a sharp 
point. The parts near the joint of the wire to the rod is heavily 
taped, partly to form an insulating handle for the operator and 
partly to prevent localization of bending at the junction, which 
would result in an early break. The object in providing the rods 
with sharp points is to permit an exceedingly high pressure in 
proportion to the area of contact being obtained, which will in¬ 
sure metallic contact in spite of any film of oxide or dirt with 
which the metal surfaces may be covered. 

Instead of using current from service mains and 110-volt bulbs, 
current from a low-voltage battery, such as an ignition or car 
lighting storage battery, or a dry cell battery, may be used, to¬ 
gether with a low-voltage lamp or bulb. The arrangement is 
substantially the same as in the previous ease, the outfit includ¬ 
ing the battery, the lamp and a pair of contact pins, besides the 
necessary wiring, as shown in Fig. 339. 

A dry cell battery of five eells is somewhat more convenient 
for this work than a storage battery, mainly on account of its 
lower weight but also on account of its greater cleanliness. 
Though modern storage batteries are practically non-slopping, the 
dry-cell battery has absolutely no free electrolyte, which is bet¬ 
ter. A dry-cell battery also is better adapted than a storage bat¬ 
tery to the service of furnishing momentary currents at more or 
less extended intervals, because it deteriorates less rapidly dur- 


510 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

ing periods of non-use. Of course, where current is required more 
or less continuously and in considerable quantity, the storage bat¬ 
tery has the advantage. 

Some testers prefer devices that give an audible indication, 
and in this class belong the bell and buzzer, Fig. 340, on the one 
hand, and the telephone receiver on the other, Fig. 341. The 
handiest form of the latter type of instrument is the head re¬ 
ceiver as used by telephone operators at telephone switchboards. 
It has the advantage that it does not have to be held in the hand 
and leaves both hands free for manipulating the test points and 
making and undoing connections. Whether a bell, buzzer or tele¬ 
phone receiver is used to indicate current flow, a battery must be 
provided to furnish the operating current. A couple of dry 
cells will give a clearly audible signal with any of these devices. 



Fig. 340 —Buzzer test set 


Current indicators giving an audible indication are preferable 
to lamps, especially where continuous tests have to be made, as 
in testing out the different sections or coils of an armature. In 
bright daylight an incandescent lamp lighting up does not strongly 
impress the eye, and if the testing points are moved quickly from 
one section to another, the observer is apt to fail to notice the 
light signal. Another consideration is that the operator has to 
have his eyes on the points when establishing contact and then 
must look at the bulb to see whether it is lighted up, whereas 


















MAINTENANCE AND REPAIR 


511 


with an audible signaling device he need not remove his eyes 
from the contact points. 

Because of the low voltage of the batteries, the testing devices 
described are not well suited in case a fairly high degree of in¬ 
sulation is required. It is then better to use a testing magneto. 
This is nothing more or less than a telephone magneto with a 
bell and with two lengths of cords with test pins attached. Fig. 
342. The magneto is cranked by hand and gives a very high 
voltage which will force a current through poor connections or 
leakage paths. Such a testing magneto, if much testing has to 
be done, should be operated by two persons, a boy turning the 
crank while the tester manipulates the test points. 




Fig. 342 —Testing magneto 






































512 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Partial List of Testing Apparatus 

Hydrometer syringe, Fig. 337. 

Testing lamp, using current from service mains. Fig. 338. 

Testing lamp, using battery current, Fig. 339. 

Testing buzzer, Fig. 340. 

Testing telephone, Fig. 341. 

Testing magneto, Fig. 342. 

PART III 

Classification of Troubles—Simple Tests 

Electrical troubles may be either in the major parts of the 
electrical equipment or they may be in the wiring connecting these 
parts. There are essentially four classes of general electrical 
troubles, namely, an open circuit, a short-circuit, a ground and a 
poor connection, which latter is an in©ipient form of open cir¬ 
cuit. An open circuit is a circuit with a break or interruption in 
it at any point. Voltages of the order used for lighting and start¬ 
ing will force a current only through a continuous or unbroken 
circuit of conducting material. If the circuit is open, no current 
can flow. The most familiar forms of an open circuit are a broken 
lamp filament and a burned-out fuse. Of course, the term “brok¬ 
en circuit ’ ’ usualy is applied only if there is a break in the wir¬ 
ing outside the main parts of the system or at the connections. 
If there are any poor connections in the circuit, the result is that 
the resistance in circuit is greater than it should be and the cur¬ 
rent flow will be reduced. 

A short-circuit is a derangement of the wiring or other parts 
of the circuit which allows current from the source, that is to 
say, fom the battery or generator to return to it without flowing 
through the connecting devices such as the lamps. A complete 
short-circuit prevents current from flowing through the consum¬ 
ing device. For instance, if the two wires connecting to an in¬ 
candescent lamp are bared of insulation and twisted together 
where they enter the lamp socket, no current can flow through 
the bulb. A complete short-circuit results in an excessive cur¬ 
rent flow and a rapid drain of the battery, if not the fusing of 
the wires. A partial short-circuit, often referred to as a leak, 
may not greatly interfere with the operation of the consuming 


MAINTENANCE AND REPAIR 513 

devices but will result in the waste or loss of energy, and as such 
is objectionable. 

A ground is a metallic connection between the insulated wiring 
of the circuit and the metallic mass of the chassis or engine. A 
distinction must here be made between the two wiring systems 
used in connection with electrical equipment, the insulated re¬ 
turn system and the ground return system. With an insulated 
return or two-wire system a ground on one side of the line is 
not immediately harmful, as it does not interfere with the op¬ 
eration of the system. No battery current can flow into the frame 
of the car or engine, because there is no return path. However, 
if another ground should develop on the other side of the line, 
the two grounds together would form a short circuit which would 
drain the battery and deprive the part to which the grounded 
wires are connected of current. For this reason it is always 
desirable to keep an insulated return wiring system entirely free of 
grounds, which are really incipient troubles. In the case of 
ground return wiring, as now used with the great majority of 
lighting systems, a ground on the insulated line is really a short- 
circuit. 

It must not be understood that short-circuits, open circuits and 
grounds occur only in the wiring of a car. They may also occur 
in the different parts of the equipment. It already has been 
stated that burned-out bulbs and blown fuses are cases of open 
circuits, and there are plenty of chances for short-circuits to 
develop in such parts as the generator and starting motor. 

Suppose it is suspected that there is a short in, say, the lighting 
circuit. This can be tested out by any of the testing outfits 
already described. When all the bulbs are unscrewed from their 
sockets no current should flow through the wires connecting to 
the lamps, and if a current does flow, it proves that there is a 
short-circuit. Therefore, remove all of the bulbs from their sock¬ 
ets, close all lamp switches, open the circuit at the battery by 
removing one connector from the battery terminal and touch 
the test points to the connector removed and the other battery 
terminal as indicated in Fig. 343. We will assume the lights are 
wired on the insulated return principle, or two-wire. Then if the 
test lamp lights up when contacts are made as described, it 
proves that current can flow from one side of the circuit to the 
other though all of the bulbs are removed; consequently, there 


514 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

must be a short-circuit somewhere on the line. To locate the 
exact position of the trouble requires additional tests which will 
be described further on. 

To determine whether there is a ground on the circuit, all the 
bulbs should be left in place, the lamp switches turned on and 
the two test points connected respectively to any bare part of 
the circuit and a part of the frame. The connections are shown 
in Fig. 344. If there is no ground, no current can flow through 
the lamps, and it will not light. Now suppose there is a ground 
at A. Then the test lamp will light up and the path of the test 
current easily can be traced. It does not matter whether or not 
the ground is on that side of the lighting circuit to which the 



Fig. 343 —Method of testing for a short in a lamp circuit by a 

testing lamp 


test point is touched, the test lamp will light up in either case. 
The location of the ground also calls for either a careful inspec¬ 
tion of the whole line or for further tests. 

Open circuits always manifest themselves in an unmistakable 
manner. For instance, if there is a break in a lamp circuit, the 
lamp cannot burn. If the break is in one of the main wires, of 
course all the lamps will go out, whereas if the break is in one 
of the branch circuits, only the lamp or lamps on that particular 
branch will become extinguished. Thus some indication as to the 
location of the trouble is furnished by its effects. 















MAINTENANCE AND KEPAIK 


515 


About the only test that needs to be made on the battery is 
the hydrometer test. Normally this shows the state of charge of 
each cell. Failure of the battery to maintain its charge is, of 
course, responsible for a great many difficulties. A battery 
cannot keep its charge unless it is kept filled with electrolyte to 
the tops of the plates. No fresh electrolyte needs to be added, 
however, as all loss by evaporation consists solely of water. 
Therefore, if the electrolyte does not cover the plates, distilled 
water should be added until the plates are completely covered. 
There is, of course, a bare possibility of some sulphuric acid be¬ 
ing lost by a cell, as by failure of the tester to replace the elec¬ 
trolyte withdrawn for making an hydrometer test. To make a 
conclusive test as to the density of the electrolyte, the battery 



^ .-a 


Fig. 344 —Method of testing for a ground in a lamp circuit by a 

testing lamp 


should be charged and the charging operation continued at a 
moderate rate until three or four successive hydrometer tests 
at intervals of 10 minutes show no further increase in the density 
of the electrolyte. Then the battery is completely charged. Dif¬ 
ferent battery makers are somewhat at variance as to the density 
which should be indicated under this condition, but 1.280 to 1.300 
is a good average figure. If the hydrometer shows less, remove 



















516 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

some of the electrolyte with the syringe and replace with electro¬ 
lyte of extra strength. If it shows more, replace with distilled 
water. 

Some precautions must be observed in making hydrometer tests 
to be sure of accurate results. Readings never should be taken 
immediately after distilled water has been added to the cells, as 
it is most unlikely that the water added is distributed uniformly 
throughout the old electrolyte. Make a test before adding the 
water and again after the water has been added and the battery 
charged. It is, of course, not sufficient to make a test of one cell 
only and take it for granted that the condition of the others is 
the same. Each cell should be tested separately. To avoid omis¬ 
sions, it is well always to start with the cell at the positive end 
of the battery and test all cells consecutively, returning the elec¬ 
trolyte drawn from any cell to that same cell. In taking the 
reading, it is well to see that the hydrometer does not contact 
with the wall of the syringe but floats centrally therein so as not 
to impair the accuracy of the indication. 

The hydrometer test only shows the state of charge of the bat¬ 
tery. It is desirable always to have the battery as near to the 
state of complete charge as consistent with the conditions of cur¬ 
rent demand, because battery elements deteriorate least when 
fully charged. When a battery is chronically in a state of un¬ 
dercharge, it may be due to a fault in the battery, due to exces¬ 
sive current demand, due to conditions of operation admitting 
of little charging or due to derangement in the circuits or the 
charge control system. The most common fault in the battery 
is sulphated plates, which can be detected by inspection. A 
normal positive plate when the cell is charged has a chocolate 
brown color, but when sulphated the plate has a grayish color. 
The sulphates can be reduced by repeatedly charging and dis¬ 
charging the cell at a very low rate. Lead sulphate when not 
disturbed for some time hardens and prevents circulation of the 
electrotype, with the result that charging—which means the re¬ 
duction of the sulphate to spongy lead and lead oxide—can pro¬ 
ceed only at a very slow rate. 

Open circuits and short-circuits are also possible in storage 
batteries. An open circuit most likely would be due to a cor¬ 
roded terminal and a short-circuit to a large collection of sedi¬ 
ment reaching to the lower edge of the plates and bridging same. 


MAINTENANCE AND REPAIR 


517 


The former can be detected by a careful inspection; the latter 
will be indicated by an absolute failure of a cell to hold a charge, 
as shown by a hydrometer or a voltmeter test. 

Occasionally a generator fails to pick up, that is, to start to 
generate. This is generally due to poor electrical contact be¬ 
tween the commutator and the brushes. This in turn may be 
due to dirt on the commutator, a rough commutator, insufficient 
spring pressure on the brushes, etc. The simplest test is to press 
the brushes down on the commutator by hand. In case the trou¬ 
ble is with the brushes, this may cause the generator to pick 
up, as with increasing pressure on the brushes the brush contact 
resistance decreases. A permanent repair, of course, involves 
the elimination of the cause of the trouble. 

If the commutator is very rough, it should be turned down in 
the lathe and sandpapered. If it is merely dirty, sandpapering 
alone will do, while if the spring pressure is too small, which is 
probably due to the brushes being nearly worn out, the latter 
should be replaced. Of course, failure to pick up may be due to 
other and more serious causes, such as a break in the field cir¬ 
cuit, a burned-out armature, etc. The generator field readily 
can be tested by a test lamp or test bell, by disconnecting it from 
the generator terminals. If the lamp lights or the bell rings 
when the test points are touched to the end of the field winding, 
it shows that there is no break in the field circuit, and if the test 
lamp fails to light up or the bell to ring when one test point is 
touched to a part of the field winding and the other to the frame 
of the car, it shows that there is no ground in the field circuit. 

One method of testing out a generator that will not pick up 
is to remove its driving connection, so it can rotate independently 
of the engine crankshaft, and then close the automatic switch 
or battery cutout by hand. This connects the generator to the 
battery and causes it to act as a shunt motor. If poor brush con¬ 
tact was the cause of its failure to pick up, this would not 
prevent its operation as a motor, as the battery voltage will 
easily force enough current through the brushes to cause the 
armature to revolve. If there is nothing wrong with either 
the field winding or the armature, the generator should turn 
over at about the lowest speed at which it will charge the bat¬ 
tery when driven by the engine—just a trifle lower than this. 


518 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


PART IV 

Testing Out Complete Circuits 

If an ammeter is available and the tester has any data re¬ 
garding the normal performance of the system under test, it can 
be used to advantage in locating the fault. Most makers of 
electrical equipment issue and publish in their catalogs, or in¬ 
struction books, so-called generator output or charging curves, 
showing the number of amperes the generator will send into the 
battery at different speeds of revolution. If such a curve is at 
hand, or if the normal charging rate at a definite generator speed 
is known, the ammeter can be used to determine whether the 
generator is delivering its proper charging current. Inasmuch 
as the charging current with most systems above a certain mini¬ 
mum generator speed is substantially constant, it does not mat¬ 
ter very much at what generator speed the reading is taken, pro¬ 
vided it is above the minimum speed referred to. This mini¬ 
mum speed of the generator at which charging begins corresponds 
to a certain car speed on the high gear, usually about 7 or 8 
m.p.h., and the tester may be able to tell from the sound of the 
engine whether it is running at a speed above that at which 
charging begins. The charging circuit then is opened at the 
battery and the ammeter is inserted in the circuit at this point. 
All lamps are turned off. A reading then is taken of the charg¬ 
ing current, and if it agrees with the generator output diagrams, 
there is nothing the matter with the generator, its control mech¬ 
anism and wiring. 

In that case, the trouble, if the battery will not hold its charge, 
must be in the distributing circuits or in the battery itself. A 
similar test can be made of the lamp load. Generally the current 
consumed with all the lights turned on is given in the descrip¬ 
tive matter of the equipment makers. If it cannot be found, it 
can he calculated fairly accurately from the voltage and candle- 
power of the lamp. 

Supposing the lighting equipment to operate at 6 volts and the 
lamps to be of the tungsten filament vacuum type, the head¬ 
lamps will consume each about 1/6 ampere per candlepower and 
the small lamps about % ampere per candlepower. 

Thus if there are two 15-eandlepower headlights, two 4-can- 
dlepower side lamps and one each 2-candlepower tail and dash- 


MAINTENANCE AND REPAIR 


510 


lamp, the total current consumption when all are turned on should 
be 7.4 amperes. If the current consumption is greater, it may 
be due to bulbs of high candlepower being used by mistake or 
to a short-circuit or leak on the line. If the current is smaller 
than it should be, it may be due to some lamps not burning or to 
the use of bulbs of too low candlepower or of high-efficiency bulbs. 
If some lamps are not burning, this may be due to a broken 
filament, to the bulb being loose in the socket, to a burned-out 
fuse or to a broken wire or connection. 

It is, of course, entirely unnecessary to make a test with 
instruments requiring disconnections in the circuits, to find out 
that a lamp does not burn. Usually, if a single lamp fails to 
light up, it is due either to a broken filament, a bulb loose in 
the socket or a fuse blown out. If a lamp fails to light up when 
the switch is closed, see whether it is tight in the socket. If it 
is not, screwing it home probably will cause it to light up. On 
the other hand, if it is tight in the socket, the filament probably 
is broken, which readily is proved by substituting a new bulb 
known to be in good condition. Often the wire connections at 
the lamps come loose, and if neither a loose bulb nor a broken 
filament is found it is well to inspect these connections carefully. 
In the case of a ground return or single-wire system, with all the 
sockets grounded on one side, it is well to test the ground of the 
faulty lamp by making a connection with a screwdriver or a 
length of wire from the lamp terminal to ground, a bright part 
of the frame. If this causes the lamp to light up it shows the 
ground connection to be faulty. 

A frequent cause of failure of lamps to light up is a fuse burned 
out. Fuses are safety devices inserted in practically all elec¬ 
trical circuits. They are the safety links which give out first 
in case of excessive currents due to short-circuits or other causes, 
thus protecting the rest of the circuits against injury. The type 
of fuse most commonly used in motor car circuits is the so-called 
cartridge fuse, which consists of a short length of glass tube 
with brass ferrules at both ends, these ferrules being connected 
metallically by a lead wire inside the glass tube. The complete 
fuse is pressed between brass clips on the fuse block. These fuse 
blocks are located in different positions on different makes of cars, 
but they always are to be found somewhere. If a fuse is blown 
due to a short-circuit, as soon as another fuse is inserted it, too, 


Fig. 345 —A typical wiring system 


520 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 







































































MAINTENANCE AND REPAIR 


521 


blows. Therefore, before inserting another fuse it is well to test 
for a short-circuit. Fuses occasionally burn out in regular service 
or as a result of momentary short-circuits, such, for instance, as 
occasioned by working on junction blocks, etc., with a screw¬ 
driver while the current is on. 

The quickest way to test for a blown fuse in a lamp circuit is 
to turn the lamp switch oh and then place the blade of a screw¬ 
driver across the fuse clips. If the lamp lights up with the fuse 
clips bridged by the screwdriver and does not without it, the fuse 
is burned. If there happened to be a short-circuit on the line, this 
test will be accompanied by violent sparking at the fuse clips, 
or, as a repairman would say, by a display of fireworks. 

In trying to locate either a ground, an open circuit or a short- 
circuit in a wiring system it is advisable to divide the system into 
its various elements or circuits. A typical wiring system is illus¬ 
trated in Fig. 345. There are only two wires connecting to the 
battery, and these, therefore, carry all the current that flows into 
or out of the battery, whether it is charging current or whether 
it is battery current for starting or for lighting. It will be seen 
that this is a two-wire, or insulated return, wiring system, and a 
test for a ground can be made merely by touching test points to 
any bare part of the wiring and a bright spot on the metallic mass 
of the chassis respectively. 

We will assume now that a general test of the wiring is to be 
made. Each of the lamp circuits begins at the lamp switch. The 
headlamp circuit ends at 1, though from 5 to 1 the wire carries 
both battery current for the headlamps and charging current for 
the battery—alternately, of course, not simultaneously. To make 
a test of the headlamp circuit the generating system must be 
disconnected from it, and this probably can be done best by 
loosening the connection at the minus terminal of the cutout. 

Now with the test points touching the ends of the headlamp circuit 
at point 7, at the lamp switch and at point 1. If the test lamp 
lights up or the test bell rings, the headlamp circuit is complete, 
that is, there is no open circuit. Now remove the bulbs from the 
headlamp sockets and make another test with the test points in 
the same way. If current flows, it shows a short in the headlamp 
circuit. To locate a ground, touch one of the test points to the 
ends of the headlamp wires, first at 1 and then at 7, while the 
other test point is connected to ground, that is, some bright spot 


522 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

of the frame, etc. If a signal is obtained, it shows not only a 
ground in the headlight wiring but also the side of the headlight 
circuit on which the ground is located. 

The tests thus described show any fault in the wiring leading 
to the two headlamps. If a fault thus is found to exist, it should 
be attempted to locate it by a careful inspection of the wiring. 
There is, of course, a possibility of determining by electrical tests 
still more closely the location of the fault, as by disconnecting 
the wiring for one lamp from that for the other, at 3 and 4, and 
testing the wiring for each lamp separately. However, unless ab¬ 
solutely necessary, no permanent joints in the wiring should be 
opened. Usually the wiring system can be divided sufficiently 
by undoing the bolted or binding post joints at the switch, junc¬ 
tion box, etc. Thus, for instance, if the joint 2 in the diagram 
is a permanent joint, the circuit can be opened at the ammeter a 
little farther along the line to the headlamps. 

The dashlamp circuit begins at 9 at the lamp switch and ends 
at 11 on the battery main. The taillight circuit is connected to it at 
12, and this connection must be broken if it is desired to make tests 
of tho dashlamp circuit separately. The tests are exactly the same 
as those for the headlamp circuit and need not be described 
specially. The tail light circuit begins at 8 at the lamp switch and 
ends at 12. 

That part of the circuit which carries current from the gen¬ 
erator to the battery only begins at 2 and ends at 5. This circuit, 
when the generator is not running, is interrupted in the cutout and 
if it is desired to make a test of the whole circuit for shorts, 
breaks, etc., the cutout should be held closed by hand. Also, if 
2 and 5 are permanent joints, the tests can be made between 13 
and 14. 

There remains only the starter circuit to be tested. As a rule, 
this contains only short lengths of very heavy wire, and it is 
easier carefully to inspect every part of it than to disconnect it 
completely from all other circuits and make electrical tests. If 
the inspection fails to locate the fault, an electric test, however, 
can be made as a last resort. 

In making the different tests described with the aid of a wiring 
diagram it is well to check off the individual circuits on the dia¬ 
gram as they are tested. In this way one cun be much more cer- 


MAINTENANCE AND REPAIR 523 

tain that he has covered every part of the system when the test 
is ended. 

If there is a break somewhere in a circuit, by a test lamp or 
bell the particular section of the circuit in which the break is 
located easily can be found. Suppose the circuit has been isolated 
from the rest of the wiring system. Place one test point on the 
end of one side of the circuit at the point farthest from the lamp 
or other consuming device. With the other test point touch the 
first exposed point on the same side of the circuit toward the 
consuming device. If the test lamp does not light up, the break 
is in this section; if it lights up, this section is intact, and the 
test point should be moved to the next exposed point, and so on 
all around the circuit. When a point is reached where the test 
lamp shows no light, the break is in the section between this 
point and the point touched immediately previously. 

Applying this to the charging circuit of the wiring system illus¬ 
trated in Fig. 345, one test point may be connected to point 5 of 
the system and the other test point would be touched first to point 
14. Probably the test lamp would light up. Next it would be 
touched to the negative terminal of the generator with say, the 
same result; next to the positive terminal of the generator with 
the same result; next to point 15 with the same result; next to 
point 16, when it would show no current flow. The break in the 
circuit then would be between points 15 and 16 and probably would 
be due solely to the open cutout, which is not a fault but a natural 
condition. In this connection it must be remembered that between 
points 14 and 15 there are two paths for the current, namely, 
through the generator and through the shunt coil or fine wire coil 
of the cutout. Therefore, to make the test conclusive, the wire 
should be removed from terminal 15 while this terminal is touched 
—to test the shunt coil of the cutout—and while the test wire 
is touched to the two terminals of the generator and to the end of 
the wire removed from 15 respectively. 

One test of a faulty starter is as follows: Switch on all the 
lamps, close the starter switch and observe the behavior of the 
lamps. If there is no effect on the lamps, it shows that no current, 
or only a very small current, flows through the starter, so that 
not enough turning effort to crank the engine could be expected. 
On the other hand, if the lamps grow appreciably dim as the 
starter switch is closed, it shows that a heavy current flows into 
the starter, and if the latter does not crank the engine, the indi¬ 
cation is that either the field or the armature is short-circuited. 


CHAPTER XXX 


Stock Ford Ignition and Lighting System 


HE ignition and lighting system used on the Ford car as 



1 standard equipment is decidedly different from any other 
system now in use and it is deserving of a thorough description 
on account of the many systems in service. 

Electrical energy is obtained from a specially constructed mag¬ 
neto, which consists of sixteen coils of flat copper ribbon wound 
around sixteen equally spaced iron cores, which are mounted on 
a special structure bolted to the transmission case directly in 
front of the flywheel. Sixteen small permanent horseshoe mag¬ 
nets are mounted on the front face of the flywheel, and just 
enough clearance is allowed between the pole-pieces of these per¬ 
manent magnets and the iron cores about which the copper coils 
are wound to prevent them from striking when the flywheel is 
caused to rotate. The coils and their mounting are shown in 
Fig. 4. The sixteen magnets and the method of mounting them 
are shown in Fig. 5. The magnets are so placed relative to each 
other that adjacent ends are of the same magnetic polarity, and 
these two ends are joined magnetically, so as to form a single 
magnetic pole, by a clamp of magnetic material. There are then 
sixteen magnetic poles around the outer edge of the flywheel, and 
these poles are alternately of north and south magnetic polarity. 

When the magneto is assembled and the magnetic poles are 
directly opposite the iron core of the coils, there will be mag¬ 
netic lines of force across the gap between the poles and the 
iron cores, and the direction of these lines of magnetic force 
will be from the north magnetic poles across the gap, through 
the iron core under the north poles, through the structure sup¬ 
porting the iron cores to the cores under the south poles of the 
magnets, up through these cores across the air gap to the south 
magnetic poles, thence through the magnets to the north mag¬ 
netic poles, which completes the magnetic circuit or path of the 
lines of magnetic force. With the magnetic poles directly op- 


STOCK FORD IGNITION AND LIGHTING SYSTEM 525 


posite the iron cores of the coils, there is a maximum number 
of lines of magnetic force through the coils, since the magnetic 
circuit with the various parts in this relation to each other offer 
a minimum opposition to the production of lines of force. The 
direction of the lines of force through eight of the coils will be 
from the north magnetic poles on the permanent magnets through 
the coils toward the support for the iron cores, and the direction 
of the lines of magnetic force through the remaining eight coils 
will be from the support for the iron cores toward the south 



Huagneto coil 

L SPOOL 

; COPPER 

WIRE 

TO 

END OF 
RIBBON 

HERE 

MAGNETO 
SUPPORT 




COIL 


MAGNET 
FLYWHEEL 
MAGNET CLAMP 


Figs. 4 and 5 —Stationary coils of Ford magneto mounted on 
metal coil support, left, and permanent horseshoe magnets 
mounted on front face of flywheel 


magnetic poles on the permanent magnets. Now, if the magnetic 
poles be moved so that they are midway between the iron cores, 
there will be a minimum number of magnetic lines through the 
coils as this position of the magnets and the iron cores offers a 
maximum opposition to the production of lines of force. If 
the magnetic poles be moved farther on so that they are again 
opposite the iron cores, the magnetic lines through the coils 
will again have a maximum value. The direction of the mag- 




526 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

netic lines through the coils in this last position will be in just 
the reverse direction to what it was in the first position, since 
the north magnetic poles are now opposite iron cores, which 
originally had south magnetic poles opposite them, and south 
magnetic poles are now opposite iron cores which originally had 
north magnetic poles opposite them. 

If the magnetic poles be advanced another sixteenth of a rev¬ 
olution, the polarity of the magnetic poles and iron cores will be 



__I_ 

% INVOLUTION 


Fig. 6 —Variation in magnetic lines through coils for different 
positions of magnetic poles with reference to iron cores on which 
coils are wound 

the same as at the beginning. Hence, the magnetic lines through 
any particular coil pass from a maximum value in one direction 
through the coil to zero value, build up to an equal maximum 
value in the opposite direction through the coil, then to zero value 
and increase to a maximum value in the same direction as it 
originally had, while the magnetic poles are moving from a posi- 























STOCK FORD IGNITION AND LIGHTING SYSTEM 527 

tion directly opposite the iron cores through an eighth of a rev¬ 
olution. The variation in the value of the number of magnetic 
lines through the coils for different positions for an eighth of a 
revolution is shown in Fig. 6. The distance of the heavy curve 
marked magnetic lines above or below the horizontal line 00 is 
a representative of the value of the number of magnetic lines 
through the coils for the different positions. Thus for position 
marked A the magnetic poles are opposite the iron cores and the 
value of the magnetic lines is a maximum. For position B the 
magnetic poles are midway between the iron cores, and the value 
of the magnetic lines through the coils is zero. For position C 
the magnetic poles are again opposite the iron cores, but the 
polarity of the magnetic poles in relation to the iron cores is 
just the reverse of what it was for position H, and, hence, the 
value of the magnetic -lines through the coils will have a maxi¬ 
mum value for position A. The magnetic lines through the coils 
are zero in value for position D and again reach their original 
maximum value for position E. 

As a result of the magnetic lines of force through the cores 
changing in value an electrical pressure will be generated in the 
different coils, and the direction of the generated pressure in 
adjacent coils will be in the opposite direction around the coils, 
since the magnetic lines pass through adjacent coils in opposite 
directions. The coils, however, are so connected that the electrical 
pressures all act in the same direction and the total electrical 
pressure between the terminals of the magnetos at any instant is 
equal to the sum of the electrical pressures in the sixteen coils. 
The value of the electrical pressure in each coil at any instant 
will depend upon the number of turns in the coil and the rapid¬ 
ity with which the magnetic lines through the coil are changing. 
An inspection of the curve in Fig. 6, which shows the varia¬ 
tion in the magnetic lines through the coils for different positions, 
will show that the electrical pressure is zero when the magnetic 
lines are a maximum and that the electrical pressure is at a 
maximum when the magnetic lines through the coils are equal to 
zero, etc. These results can be explained as follows: Suppose 
we take a small part of a revolution, such as l/144th, as shown at 
F in the figure. For this small part of a revolution, the magnetic 
lines increase in value from zero to GH. For the next l/144th, 
of a revolution they increase in value from GH to IJ, or the 
net increase is KJ. It is thus seen that the net increase in mag- 


528 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

netic lines is growing less for each l/144th of a revolution, until 
the magnetic lines through the coils have reached their maximum 
value when the net increase is zero. 

As the magnetic lines through the coils decrease in value, the 
rapidity with which they are changing in number increases 
until the lines through the coils are equal to zero, when the 
rapidity of their change in number reaches its maximum value 
and then starts to decrease and again becomes zero when the 
lines through the coils have reached their maximum value. As 
a result of this varying rapidity with which the lines through 
the coils are changing, a varying electrical pressure will be 
produced in the coils. The induced electrical pressure may be 
represented by a curve having the form of the dotted curve, in 
Fig. 6. The electrical pressure produced in the coils while the 
magnetic lines are decreasing in value in one direction through 
the coils will be in the same direction as the electrical pressure 
produced in the coils while the magnetic lines are increasing in 
value through the coils in the opposite direction. 

Such a pressure as the one shown in Fig. 6 is called an 
alternating pressure, because it is first in one direction and then 
in the other. All values of electrical pressure, represented 
above the horizontal line 00, are considered positive and all 
values below the line are considered negative. A complete sys¬ 
tem of positive or negative values is called an alternation, and 
the complete alternation constitutes what is called a cycle. In 
the Ford magneto there are sixteen alternations per revolution 
and eight cycles per revolution. If this alternating pressure is 
connected in a closed electrical circuit, it will produce an alter¬ 
nating current in the circuit and the current will complete the 
same number of cycles in a given time as the electrial pressure 
completes. The number of cycles the electrical pressure and 
current complete in a second is called the frequency of the pres¬ 
sure and current. The frequency of the electrical pressure de¬ 
veloped by the Ford magneto will be equal to eight times the 
number of revolutions of the flywheel in a second. 

Magneto Terminal Connections 

One terminal of the circuit formed by connecting all the six¬ 
teen coils in series is grounded permanently by connecting it to 
the metal support for the iron cores, which in turn is bolted to 


GROUND CONNECTION 


STOCK FOED IGNITION AND LIGHTING SYSTEM 529 



FORD MODEL T 

Fig . 7 —Wiring diagram of standard equipment on a Ford 













































530 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the transmission case. The remaining terminal is connected to 
an insulated binding post mounted on top of the transmission 



Fig. 8 —Perspective view of wiring and component parts of Ford 
standard electrical equipment 


case. The terminals of the magneto, then, are the insulated bind¬ 
ing post and the ground connection. 


Ignition System 

The ignition for the Ford car is taken care of by a four-unit 
induction coil mounted on the dash and so arranged that energy 
may be supplied to its primary winding from either of two 



















STOCK FORD IGNITION AND LIGHTING SYSTEM 531 


PULL ROD 
CONNECTION 


COMMUTATOR 
ROLLER- 

CONTACT- 
POINT 

CAM 
SHAFT 


COMMUTATOR 
ROLLER ARM 


ALUMINUM casing 
THUMB NUT> 



FIBRE BED' 

Fig. 9 —Interior of Ford timer 


sources, depending upon 
the position of the igni¬ 
tion switch. The only 
source of electrical 
energy provided by the 
manufacturers of the car 
is the magneto, but a bat¬ 
tery connection is pro¬ 
vided in the coil box and 
may be used merely by 
grounding one terminal 
of the battery and con¬ 
necting the other term¬ 
inal to the binding post 
on the coil box. 



A wiring diagram of 
the lighting and ignition 
system supplied as stand¬ 
ard equipment on the 
Ford car is shown in Fig. 
7, and the relative loca¬ 
tion of all the different 
parts, together with their 
various electrical connec¬ 
tions, is shown in Fig. 8. 
The four primary igni¬ 
tion circuits may be 
traced as follows: Start¬ 
ing with the magneto 
contact, along the in¬ 
sulated wire to the magneto terminal on the coil box, then to the 
magneto contact on the switch on the front of the coil box, and 
when this switch is closed on the magneto, all the primary windings 
are connected to the magneto contact but the circuits through these 
various windings are closed one at a time and in a definite order by 
the commutator, or timer, which grounds the different wires as the 


Fig. 10 —Connections of special dim¬ 
mer and leads to special switch on steer ■> 
ing post 


roller contact in the timer makes contact with the terminals to 
which the different wires are connected. The interior construc¬ 
tion of the timer is shown in Fig. 9. When a battery has one 

























532 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

terminal grounded and the other terminal connected to the bat- 
ery terminal on the coil box and the switch on the .front of tne 
coil is thrown in the position marked battery, the battery replaces 
the magneto as a source of electrical energy and all she other 
operations remain the same. 

A vibrator is connected in series with each of the primary 
windings, and when any one of the primary wires leading to the 
tinier is grounded the vibrator in that particular primary cir¬ 
cuit will vibrate as long as the circuit is closed, which will cause 
a high voltage to be induced in the secondary windings sur¬ 
rounding the primary winding of the induction coil. One ter¬ 

minal of each of the four secondary windings is grounded, and 
the remaining four terminals are connected to the four spark 
plugs by suitable lengths of high-tension wire, as shown in Figs. 
7 and 8. The primary wires leading from the induction coil 
to the timer are marked with colored threads as shown in Figs. 
7 and 8. 

Lighting Circuit 

The lighting circuit for the headlights may be traced as fol¬ 
lows: From the magneto contact to the magneto terminal on 
the coil box, then to the lamp switch on the dash, through the 

switch when it is closed, then to the right-hand headlight and 

through the bulb, then to the left-hand headlight and through the 
bulb, then to ground and through the winding of the magneto 
to the magneto contact which completes the circuit. The two 
headlight bulbs are in series and if they are alike, approxi¬ 
mately half of the electrical pressure generated in the winding 
of the magneto will act on each of the lamps, the remainder 
being used in overcoming the resistance of the winding of the 
magneto, the resistance of the connecting wires, ground connec¬ 
tions, switch contact resistance-, etc. 

Horn Circuit 

The horn circuit may be traced from the magneto contact to 
the magneto terminal on the coil box, then to the horn, through 
the horn to the horn button mounted on the steering post, through 
the horn button when it is closed to ground, through the winding 
of the magneto to the magneto contact which completes the 
circuit. 


STOCK FORD IGNITION AND LIGHTING SYSTEM 533 


Combination Switch and Dimmers 

The Ford company is equipping its cars now with a combina 
tion horn and light switch, which is mounted on the steering 
column and has very much the same general appearance as the 
horn button except the switch is longer to provide the neces¬ 
sary space for the various additional contacts and terminals. In 
addition to the combination horn and light switch, the Ford 
company is providing a means of dimming of the headlights. 
The dimmer consists of a coil of wire wound about a laminated 
iron core and so arranged that it may be connected in series 
with the headlights by a special switch on the steering post. 

The special switch is so constructed that a small pressure on 
its rounded top closes the horn circuit and a small rotation from 
its normal position connects the lamps to the magneto with the 
dimmer coil in circuit and a further slight rotation connects the 
lamps directly to the magneto. The electrical connections of 
this special switch are shown diagrammatically in Fig. 10. 
Pressing the switch connects wires A and B, rotating the switch 
to the second position connects wires A and D and rotating it to 
the third position connects wires A and C. The light circuit 
is entirely open with the switch in the first position. When 
the switch is in the second position and the wires A and D are 
connected, the winding on the dimmer is connected in series 
with the lamps. The action of this coil is dependent upon a 
combination of the resistance of the coil and a property of the 
coil called its inductance. The effect of the inductance of the 
coil depends upon the frequency of the current in its windings, 
and this effect increases with an increase in frequency and de¬ 
creases with the decrease in frequency. 

If the engine speeds up there is an increase in the frequency of 
the generated electrical pressure, and also an increase in the 
value of the electrical pressure, but the increase in electrical pres¬ 
sure is offset to a certain extent by the increase in the effect of 
the inductance due to the increase in frequency and the current 
through the lamp will remain nearer constant in value than it 
would if a resistance alone were used. 

Ignition Trouble 

The uneven sputter and bang of the exhaust means that one 
Or more cylinders are exploding irregularly or not at all and that 


534 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the trouble should be treated promptly and overcome. Misfiring, 
if allowed to continue, will in time injure the engine and the 
entire mechanism. If you would be known as a good driver, 
you will be satisfied only with a soft steady purr from the ex¬ 
haust, and if anything goes wrong, stop and fix it if possible 
rather than wait until you get home. 

A missing cylinder can be detected by manipulating the vibra¬ 
tor on the spark coils. Open the throttle until the engine is 
running at a good speed and then hold down the two outside 
vibrators, Nos. 1 and 4, with the fingers, so they cannot buzz. 
This cuts out the two corresponding cylinders, No. 1 and 4, leav¬ 
ing only Nos. 2 and 3 running. If the two cylinders, Nos. 2 and 3 
explode regularly, it is obvious that the trouble is in either cylin¬ 
der No. 1 or No. 4, or both. Now relieve No. 4 vibrator and hold 
down No. 2 vibrator and No. 3 vibrator and also No. 1 vibrator. 
If No. 4 cylinder explodes evenly, it is evident the trouble is 
in some other cylinder. In this manner all the cylinders in turn 
may be tested until the trouble is located. Examine the spark 
plug and vibrator of the cylinder in trouble. 

The gap in the spark plug should be approximately ^ inch 
in length and the plug should be free from an undue accumula¬ 
tion of grease and carbon. If the points in the vibrator are 
pitted, they should be filed flat with a fine double-faced file and 
the adjusting thumb nut turned down so that with the spring 
held down, the gap between the points will be a trifle less than 
inch. Then set the lock nut so that the adjustment cannot be 
disturbed. Do not bend or hammer the vibrators, as this would 
effect the operation of the cushion spring on the vibrator bridge 
and reduce the efficiency of the unit. 

If with the vibrator properly adjusted and the plug cleaned 
and adjusted the cylinder still fails to operate, then examine 
the wiring and connections carefully for loose connections and 
open circuits. The coil itself may be tested by changing it and 
some other coil which is operating correctly. If the cylinder 
still fails to operate properly after making the above tests, 
the trouble is probably due to an improperly seated valve, worn 
timer or short-circuit in the timer wiring. The valves in each 
cylinder may be tested by lifting the starting crank slowly the 
length of each cylinder in turn, a strong or weak compression 
in any particular cylinder easily being detected. It sometimes 
happens that the packing between the cylinder head and the 


STOCK FORD IGNITION AND LIGHTING SYSTEM 535 


cylinder becomes leaky, thus permitting the gas under compres¬ 
sion to escape, a condition that can be detected by running a lit¬ 
tle lubricating oil around the edge of the packing and noticing 
whether bubbles appear or not. 

The surface of the circle in the timer around which the roller 
travels should be clean and smooth, so that the roller makes a 
perfect contact at all points. Should the roller fail to make a 
good contact on any one of the four contact points, its correc- 
ponding cylinder will not fire. The surfaces should be cleaned 
with gasoline. In case the fiber, contact points and roller of the 
timer are badly worn the most satisfactory remedy is to replace 
them with new parts. The spring in the timer should be strong 
enough to make a firm contact between the roller and the four 
contact points, as the roller is made to rotate by the gearing con¬ 
necting it to the engine. Carefully inspect the four wires lead¬ 
ing from the primary terminals of the coil box to the four bind¬ 
ing posts on the timer to see that they are not shorted or broken 
and that the ends at the timer are not in contact with the case, 
thus causing a more or less perfect ground connection. 

Oil Troubles 

In very cold weather the very best grades of oil are likely to 
congeal to some extent, and if this happens the roller may be pre¬ 
vented from making perfect contact with the contact points em¬ 
bedded in the fiber. To overcome the possibilities of an occur¬ 
rence of this kind and also to prevent the contact points from 
rusting, a mixture of 25 per cent kerosene with the commutator 
lubricating oil is recommended, which will thin it sufficiently to 
prevent congealing or freezing, as it is commonly called. 



1924 Model Ford Sedan 
























CHAPTER XXXI 


F. A. Starting and Lighting System for 
Ford Cars 

A LAEGE percentage of the Ford cars are at the present time 
be’ng equipped at the factory wih a specially designed 
starting and lighting system. This system has been developed to 
meet the particular requirements of the Ford car and the neces¬ 
sary changes in the engine housing have been made by the Ford 
Co. so as to accommodate the system in the best way possible. 
The system is known commercially as the F. A. Starting and Light¬ 
ing System, the initials being those of the engineer designing the 
system. 

Component Parts of the F. A. Starting and Lighting 

System 

(a) Generator 

(b) Storage Battery 

(c) Cutout 

(d) Ammeter 

(e) Starting Motor 

(f) Starting Switch 

(g) Lamps 

(h) Combination Switch 

(i) Connecting Leads 

Function and Description, of Each of the Component 
Parts of the F. A. Electrical System 

(a) The Generator 

The generator is a machine for converting mechanical energy 
into electrical energy. The mechanical energy is produced by the 
gas engine and it is in turn transferred to the generator through 
a suitable train of gears, chain, belt or other suitable mechanical 
connecting link. The electrical energy delivered by the generator 
may be used in operating the lamps on the car, in operating the 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


533 

ignition system, in charging the storage battery, etc. In each case 
the electrical energy delivered by the generator is transformed into 
some other form of energy. For example, in the ignition system 
the electrical energy is transformed into heat energy in the spark 
between the points of the spark plugs which is of sufficient inten¬ 
sity to raise the gas around it to the ignition point and as a re¬ 
sult the gas mixture in the cylinder is exploded. In the case of 
the storage battery, the greater part of the electrical energy 
delivered by the generator is transformed into chemical energy in 
the battery and as a result the battery is said to become charged. 

The frame of the generator for the F. A. electrical system is 
made from a piece of wrought iron pipe having an outside diameter 
of approximately 4.5 inches and an inside diameter of approxi¬ 
mately 3.0 inches. The length of the frame is approximately 4.5 
inches. The generator has four poles and these are formed by 
bolting four pole pieces inside the frame by means of flat headed 
machine screws which pass through the frame and into the pole 
pieces. The complete generator is shown in Fig. 346. The screws 
shown at S are the ones holding the pole pieces in place. 

Each of the four pole pieces is provided with a single field coil 
which is wound on a special form, taped and impregnated with in¬ 
sulating varnish and then placed on the field core before the core 
is bolted in place. The projections from the pole pieces serve to 
hold the field coils in place after the pole pieces are bolted to the 
frame or yoke of the machine. The four field coils are connected 
in series in such a manner that the pole pieces are alternately of 
north and south polarity around the armature. The connections 
between the various field coils are soldered and taped with an in¬ 
sulating tape. The resistance of the complete field winding at 
room temperature is approximately 3.0 ohms. 

The general features of the armature are practically the same 
as used in standard practice. There are 21 slots in the armature 
core, and 21 segments in the commutator. The winding is made 
from cotton covered enameled wire which is held in the slots by 
wedges of insulating material driven in the top of the slots after 
the winding is in place. 

The armature is mounted in. suitable ball bearings which in turn 
are carried by end' brackets bolted to the generator frame, as 
shown in Fig. 346. The front end bracket, that is, the one toward 
the front end of the car when the generator is mounted on the en- 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 539 


gine, is a flat iron disk having an outside diameter equal to the 
outside diameter of the generator frame and a pocket in its center 
containing the ball bearing for the armature shaft. This flange 
is fastened to the end of the generator frame by means of six 
cap screws shown at B. in Fig. 346. There arc three threaded 
holes in the outside face of the flange into which the cap screws 
used in mounting the generator on the engine housing are screwed. 

The rear bracket is a cup shaped piece, and it carries the rear 
ball bearing and the ring upon which the brushes are mounted. 
This bracket is fastened to the rear end of the generator frame 
by means of cap screws shown at F in Fig. 346. There are four 
openings in the cylindrical portion of this bracket through which 
the commutator, brushes, wiring and general operation of the gen- 



Fig. 346.— F. A. generator. 


Fig. 347 —F. A. generator circuit diagram. 


erator may be examined. These openings are closed by means of 
a sheet iron cover which slips over the bracket and is held in place 
by two small screws, shown at A. in Fig. 346. 

The armature winding is of the wave type and only two main 
brushes are required for conducting the current delivered to the 
external circuit to and from the commutator. These two brushes 
are mounted on the underside of the commutator as shown dia- 
grammatically in Fig. 347. The upper brush shown in the figure 
is called the third brush as the output of the generator is con¬ 
trolled by means of the “ Third Brush” principle. This third 
brush is connected to one terminal of the field winding and the 
other terminal of the field winding is connected to the mam brush 
of negative polarity as shown in the figure. The brush holder for 
the main negative brush is riveted direct to the metal brush ring 
which is in electrical contact with the end bracket thus grounding 









540 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the negative terminal of the generator. The brush holder for the 
positive brush is mounted on a small strip of insulation and this 
strip is riveted to the brush ring thus keeping the positive brush 
from making electrical connection with the frame of the generator. 
The brush holder for the third brush is mounted on the brush 
ring in such a manner that it may be moved around the com¬ 
mutator a short distance by first loosening the nut on the bolt 
supporting the holder and moving the holder to the desired posi¬ 
tion and then tightening the nut. The bolt holding the brush 
holder passes through a piece of insulation which is riveted to the 
brush ring and in which there is a slot cut thus allowing the bolt 



Fig. 348 .—Section and end elevation of generator. 


to be moved a distance around the commutator corresponding to 
the length of the slot. 

The main brush ring is fastened to the end bracket by being 
clamped between a small ring and the end bracket, the small ring 
being drawn against the end bracket by means of four screws 
which pass through the bracket from the outside through notches 
in the brush ring and into the small clamping ring. The notches 
in the main brush ring permits the ring being moved around the 
commutator a short distance so as to take care of brush adjust¬ 
ment. 

A d three of the brushes are of carbon, the two main ones are 
approximately ^-inch by ^-ineh by 34-inch an( * the third brush 


















































F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 541 





Fig. 349 .—Phantom view of generator, 





































542 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


is approximately 3/16 inch by ^-iheh by ^-inch. Electrical eon- 
nection is made from the brushes to the brush holders by means 
of flexible copper pigtails which are securely fastened to the 
brushes and the brush holders. A longitudinal section and a cross 
section of the generator are shown in Fig. 348. 



Fig, 350 —Generator in part's. 

The brushes are held firmly on the commutator by means of 
spiral springs made from flat spring steel. One end of each of 
these springs is mounted in a slot in a stud on the brush holders 
and the other end bears on the end of the brushes, see Fig. 348. 
The positive main brush is connected to an insulated terminal on 
top of the generator as shown diagrammatically in Fig. 347. 



Fig. 351 .—Diagram of generator connections. 

A phantom view of the complete generator is given in Fig. 
349 and all of the principal parts are shown in the exploded view 
given in Fig. 350. 

The generator is installed on the right-hand side of the engine 
and at the front end. Three cap screws pass through the engine 
front end cover and into the three holes in the front end bracket 
of the generator. The joint between the end bracket of the gener- 

















/ 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 543 

ator and engine cover is provided with a paper gasket to prevent 
oil leaks. 

The generator is driven by means of a pinion mounted on the 
end of the armature shaft as shown in Figs. 346 and 348, which 
engages with the large timer ge.ar. There are 16 teeth in the 
pinion and 24 in the timer gear so the generator runs at one and 
one half times engine speed. 

The relation between engine speed for different gears, miles per 
hour of the car and generator speed is given in the following table. 


Relation Between Engine Speed for Different Gears, 
Miles per Hour of Car and Generator Speed 


Hour -Model T- Generator - Model TT- 


: Car 

High 

Low 

Reverse 

Speed 

High 

Slow 

Reverse 

1 

41 

112 

163 

61 

76 

209 

305 

2 

81 

224 

325 

122 

152 

419 

609 

3 

122 

335 

488 

183 

228 

628 

914 

4 

163 

447 

651 

244 

305 

838 

1218 

5 

203 

559 

813 

305 

381 

1047 

1523 

6 

244 

671 

976 

365 

457 

1257 

1S2§ 

7 

285 

•783 

1139 

427 

533 

1466 

2132 

8 

325 

895 

1301 

488 

609 

1675 


9 

366 

1006 

1464 

549 

685 

1885 


"10 

407 

1118 

1627 

610 

762 

2094 


15 

610 

1677 

2440 

915 

1142 



20 

813 

2236 


1220 

1523 



25 

1017 



1525 

1904 



30 

1220 



1830 




35 

1423 



2135 




40 

1627 



2440 




45 

1830 



2745 




50 

2034 



3050 









544 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


Engine Speed Data 

Model T Model TT 


30 inch diameter wheel, revolution per mile- 672.27 

32 inch diameter wheel, revolution per mile- 630.25 

Gear ratio on high speed- 3.63-1 7.25-1 

Gear ratio on slow speed- 9.98-1 19.93-1 

Gear ratio on reverse_ 14.52-1 29. -1 

Revolutions of engine per mile on high speed— 2440.34 4569.31 

Revolutions of engine per mile on slow speed— 6709.25 12565.70 

Revolutions of engine per mile on reverse- 9761.36 18277.25 

MPH of car equals engine speed in RPM on 

high speed when multiplied by- 40.67 76.16 

MPH of car equals engine speed in RPM on 

slow speed when multiplied by- 111.82 209.42 

MPH of car equals engine speed in RPM on 

reverse when multiplied by- 162.68 304.62 

Ratio of crank shaft to drive shaft on slow 

speed _ 2:75-1 2.75-1 

Ratio of crank shaft to drive shaft on reverse 4.-1 4.-1 


The front bearing of the generator is lubricated by means of oil 
which spashes from the timer gear. The rear bearing is lubricated 
by oil supplied through a specially constructed oil cup mounted at 
the end of the bearing, as shown in Fig. 346. 

The value of the current delivered by the generator is regulated 
by means of the il Third Brush’ ’ system of regulation. The field 
winding is connected between the third brush which rests upon 
the upper side of the commutator and the negative main brush 
which is grounded. The value of the current delivered by the 
generator may be increased by moving the third brush in the 
direction of rotation and conversely the current output may be 
decreased by moving the third brush in the opposite direction to 
the direction of rotation. It is best to connect an ammeter in the 
circuit when an adjustment in the current delivered by the gen¬ 
erator is being made. The ammeter may be connected in the main 
circuit leading from the generator as shown diagrammatically in 
Fig. 351. Before attempting to make any adjustment in the value 
of the current delivered by the generator be sure that the com¬ 
mutator is in good condition, that the brushes are making good 
electrical contact with the commutator, that all connections in the 
generator circuit are O. K. particularly the cutout contacts, battery 
connections and the ground connection from the battery. The 









P. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 545 

voltage of the battery should be' normal, that is, there should be 
no broken down cells or high-resistance cells in the battery. 
Assuming the electrical circuit is in first class condition, with the 
exception of the position of the third brush, then you may proceed 
as follows: Run the engine at approximately 800 revolutions per 
minute and move the third brush to the position giving the desired 
value of current. The engine should then be run at different speeds 
so as to be sure that the value of the current does not exceed the 
allowable value. Xt is advisable to sandpaper the undersurface of 
the third brush after the brush has been placed in its final position 
and a final check made on the generator outfit. 

The third-brush system of control causes the current output of 
the generator to increase up to a certain speed and then the current 
output ^starts to decrease in value. The speed of the E. A. gener¬ 
ator for maximum current output is approximately 1200 revolutions 
per minute which corresponds to a car speed in high gear of approx¬ 
imately 20 miles per hour. A maximum charging current of 10 to 
12 amperes will meet the average driving conditions. 

(b) The Storage Battery 

The storage battery is composed of three cells and is known 
commercially as a six-volt sixty-ampere hour battery. The larger 
part of the electrical energy delivered by the generator is stored in 
the storage battery in the form of chemical energy which is re¬ 
transformed into electrical energy when the battery is called upon 
to operate the starting motor, ignition system, lamps, etc. 

In the earlier installations the storage battery was mounted in 
a box on the left running board, while in later cars the battery is 
under the left rear floor boards. It is carried in a frame made 
from flat iron bars, and held down by two flat pieces which press 
down on the wooden containing case at the ends, the pieces being 
held in place by thumb screws. 

(c) Cutout 

The connection between the generator and the storage battery 
cannot be a permanent one as the storage battery would discharge 
through the armature of the generator whenever the electrical 
pressure in the armature of the generator happened to be less than 


546 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

the electrical pressure of the battery. The discharge current from 
the storage battery will increase in value as the electrical pressure 
of the generator decreases in value. When the generator armature 
is standing still there is no electrical pressure induced in the wind¬ 
ing and the discharge current from the battery through the gen¬ 
erator will have its maximum value. A device called the cutout 
is introduced in the circuit connecting the generator and the 



Fig. 352 .—Complete circuit diagram, including cut-out circuits. 

storage battery whose function is to prevent the needless discharge 
of the battery under the conditions described above. 

The operation of the cutout can be understood by tracing the 
circuits as shown diagrammatically in Fig. 352. The winding A 
of the cutout is called the shunt or voltage winding as it is con¬ 
nected across the terminals of the generator and its circuit may be 
traced as follows: Starting with the positive terminal of he gen¬ 
erator you can trace along the main lead to the frame of the cutout, 
then through the winding A to the ground connection, then through 
the ground to the negative terminal of the generator and through 
the armature winding to the positive terminal thus completing the 
electrical cifcuit. As the voltage generated in the armature in- 





















F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 547 

creases in value, there will be an increase in the value of thie 
current in the winding A. The current in the winding A produces 
a magnetic pull on the armature o¥ the cutout and when this pull 
has reached a value sufficient to overcome the action of the spring 
holding the armature away from the iron core of the cutout the 
armature will move toward the core and as a result the contacts 
at C will close. As soon as the contacts at C close a second circuit 
will be completed from the positive terminal of the generator 
through the. winding D on the cutout, through the ammeter to the 
positive terminal of the battery, through the battery to the nega¬ 
tive terminal of the generator, through the armature winding of 



Figs. 353 and 354 .—Two types of automatic cut-out in diagram. 


the generator to the psitive terminal thus completing the circuit. 
The current will flow in the above circuit in the direction that the 
circuit was traced through provided the voltage of the generator 
exceeds the voltage of the storage battery. The adjustment of 
tho spring holding the armature of the cutout away from the core 
may be made in suck a manner that the armature of the cutout 
is not drawn down and the contacts C closed until the voltage of 
the generator exceeds the voltage of the battery. The connections 
of the windings A and D are such that they both produce magnet¬ 
izing actions in the same directions while the generator is charg¬ 
ing the battery. The pull on the armature is therefore increased 
as soon as the contacts at C are closed due to the pull produced by 
the charging current passing through the series winding D, and in 
































54 S 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


addition the pull is further increased due to the fact that as soon 
as the armature moves nearer the iron core of the cutout the air 
gap is decreased and the same current in the windings will produce 
a greater magnetic effect. Now if the pressure of the generator 
decreases in value there will be a decrease in the current in both 
of the windings A and D. When the generator pressure is exactly 
equal to the pressure of the battery there will be no current in the 
winding D. There will be a smaller current in the winding A than 
was originally required to close the cutout, but due to the smaller 
air gap the smaller current in the winding A will keep the contacts 
closed. A further decrease in generator pressure results in the 
battery starting to discharge and also a slight decrease in the 
value of the current in the winding A. The currents in the two 
windings are now producing magnetizing actions in the opposite 
directions and finally the magnetic pull on the armature is no 
longer ample to overcome the action of the spring tending to draw 
the armature away, and, as a result, the armature moves away and 
the contacts at C are separated thus disconnecting the battery from 
the generator. A larger current will be required in the winding 
A to again draw the armature over and as a result the contacts 
will remain separated until the voltage of the generator has built 
up to a sufficient value so that it produces enough current in the 
winding A to draw the armature over and close the contacts at 0. 

Two different types of cutouts have been used with the F. A. 
system. On a great many cars the cutout is mounted on the engine 
side of the dash board and on the right side. There are three 
terminals on the base of the cutout as shown in Fig. 353. The 
two outside terminals are insulated from the base and they are 
marked “Gen.” and “Bat.” respectively. The middle contact is 
not marked but it corresponds to the ground connection. In mount¬ 
ing the cutout on the car it is grounded to an iron strip projecting 
up from the frame of the car. 

The second type of cutout is mounted on top of the generator 
housing as shown diagrammatically in Fig. 354. The electrical 
circuits of the cutout are identical to those shown in Fig. 3-52, the 
only difference in the two being in their mechanical construction 
and arrangement. 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 549 


(d) The Ammeter 

The ammeter or charging indicator is mounted on the instru¬ 
ment board. It registers on the “charge” side when the gen¬ 
erator is charging the battery and on the “discharge” side when 
the lights are burning and the engine is not running at a greater 
speed than that corresponding to a car speed of 10 m.p.h. At a 



Fig. 355. — F. A. starter wiring 
diagram. 


Fig. 356. — F. A. starting 
motor. 


speed of over 15 m.p.h. the indicator should show a reading of 
10 to 12 amperes with the lights burning. If the indicator does 
not show “charge” under these conditions there is trouble in 
the system somewhere. The possible troubles are taken up 
further along in this chapter. When the engine is stopped and 
all lights are out the ammeter needle should come to rest at 
the O mark. 


(e) The Starting System 

The starting motor transforms the electrical energy which 
has been stored up in the battery by the generator into mechan¬ 
ical energy which is transmitted to the engine through the 
starting motor armature shaft, the Bendix drive pinion and to 
the engine flywheel, spinning the engine until it picks up and 
runs under its own power. 

The engine may be started either on battery or magneto, but 
the use of the magneto is strongly recommended, as just as hot 
a spark will be produced and the battery will have less drain 
put upon it. However, in very cold weather, when the starter 
will not turn the engine over very fast, owing to thickened oil, 
the battery will give quicker results in starting. As soon as the 
engine starts, switch to the magneto. 



550 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

The dimensions of the frame and end brackets of the P. A. 
starting motor are practically the same as those of the generator 
which has been fully described. The chief difference is in the 
construction of the end bracket at the drive end of the motor. 
This bracket is fastened to the frame of the motor by six cap 
screws. A side view of the complete starting motor is shown in 
Fig. 356. 

The armature has 21 slots and there are 21 segments in the 
commutator. 

Ball bearings are not used in the construction of the starting 
motor. The front bearing is made from a brass or bronze bushing* 
and the back bearing is made from a bushing of soft bearing 


B1 



Fig. 357 .—Circuit diagram of starter. 


metal. The bearing next to the flywheel is lubricated by oil 
splashed from the flywheel and the other bearing is not lubricated 
at all. 

Each of the four field poles carries a heavy field coil and these 
field coils are connected in series as shown diagrammatically in 
Pig. 357. There is not insulation on the joints between the field 
coils and care should be exercised to see that the bare copper does 
not come into contact with the motor frame when repairs are 
being made on the motor. The motor is of the series type, that is 
the field windings are connected in series with the armature. 
Instead of all four coils being connected in series in a single 
circuit they are grouped in two circuits of two coils each. Each 
of the positive brushes of the motor, there being two, is connected 








F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 551 


to one terminal of each of these groups and the remaining term¬ 
inals are both connected to the insulated terminal on top of the 
motor as shown in Fig. 357. 

The motor is provided with four composition brushes arranged 
as shown diagrammatically in Fig. 357. These brushes are each 
approximately ^-inch by ^-inch by^-inch. The two negative 
brushes are mounted in brush holders which are riveted direct 
to the brush ring and are therefore grounded to the frame of the 
motor as the brush ring is not insulated from the frame of the 
motor. The two positive brushes are mounted in brush holders 
which are insulated from the brush ring by mounting them on 
small strips of insulation which are in turn riveted to the brush 


COVC* SCREW 

wnsnerr 



CROSS SECTION R-R 


L O/VS / T UDINRL SECTION 

OF FTP— STRRTETt ~ 


Fig. 358 .—End elevation and section of starter. 


ring. The brushes are electrically connected to their holders by 
means of two heavy copper pigtails. The brush springs are very 
similar to those used on the generator. They are of the spiral 
type and made from flat spring steel, one end is fastened in a 
slotted stud which is part of the brush holders and the other or 
free end rests on top of the end of the brush. 

The metal ring upon which the brush holders is mounted is 
riveted to the end bracket or housing of the motor by means of 
four rivets and the brushes cannot be moved. 

A longitudinal and cross-section of the F. A. motor are shown 
in Fig. 358. The arrangement of the brushes, brush holders, etc. 
are quite clearly shown in this figure. A phantom view of the 


















































552 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 359 .—Phantom view of starter . 


























F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 553 

motor shown in Fig. 359, and an exploded view of the various 
parts is shown in Fig. 360. 

The starting motor is located on the left-hand side of the engine 
and at the rear. It is fastened to the flywheel cover by means of 
four bolts which pass through holes in the corners of the back 
end bracket. The power produced by the motor is transmitted to 
the egine by means of a Bendix drive pinion which meshes with 
a ring gear mounted on the flywheel of the engine. A cut-away 
view of the Bendix drive is shown in Fig. 361. The drive pinion 
is mounted on a hollow screw shaft, and it will move along this 
shaft if it is held from turning and the shaft is rotated. When 
a current is established in the armature and field windings of the 
starting motor its armature will start to revolve. The rotation 
of the armature shaft causes the hollow screw shaft to rotate as 



Fig. 360.— F. A. starter in parts. 

it is connected to the end of the armature shaft by means of 
the drive spring one end of which is attached to the drive head 
and the other end is connected to the screw shaft. The weight 
and inertia of the pinion tends to prevent its turning with the 
hollow screw shaft and as a result it moves lengthwise along the 
screw shaft and becomes engaged with the teeth in the ring gear 
on the flywheel. When the pinion meshes with the ring gear it 
continues to move along the screw shaft, until it comes into con¬ 
tact with the stop nut and then starts to turn the ring gear ana 
crank the engine. When the engine starts under its own power, 
it, of course, runs faster than it was being cranked by the start¬ 
ing motor and the pinion on the screw shaft is driven faster than 
the screw shaft is turning. As a result the pinion moves length¬ 
wise along the screw shaft until it is out of mesh with the gear 
on the fly wheel. The peculiar construction of the device causes 
the pinion to clutch the threaded shaft and it then rotates with 
the threaded shaft until the armature of the starting motor 









Head Spring Screw 


55 4 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 361 .—Bendix drive of F. A. starter. 




















F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 555 


ceases to rotate, due to the opening of the electrical circuit 
supplying it with current. 

By reference to the view shown in Fig. 361, and the above des¬ 
cription it is seen that the driving torque of the armature is 
transmitted to the driving pinion by means of a torsion or drive 
spring, which not only cushions the blow in starting the cranking 
of the engine, but also stores up some energy due to the running 
start while the gears are meshing, and then returns this energy 
in actually breaking the engine loose. The most difficult part of 
cranking an engine, especially in cold weather, is starting the 
engine to rotate from stand-still. 

Should the driver accidently close the starting motor circuit 



Fig 362 .—Starter switch. 


Fig. 363 .—Section of switch, 


while the engine is running no harm will result, as the pinion will 
rotate on the hollow threaded shaft until it touches the edge of 
the flywheel when it will immediately rotate in the direction of 
the threaded shaft but a little faster thus carrying it along the 
threaded shaft away from the flywheel in exactly the same manner 
as thought it was being demeshed by the engine’s starting. 

The various parts of the drive are made with large factors of 
safety so as to take care of the unusual strains they will be sub¬ 
jected to in the case of a backfire. Such an occurrence is not likely 
to happen, but it is advisable to protect *the starting system by 
retarding the spark when starting. 

There are 10 teeth on the motor pinion and 120 on the tiy- 
wneel, which results in the motor running twelve times as fast 
as the engine. 






















556 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 
(f) Starting Switch 

The function of the starting switch is to provide a convenient 
means of connecting the starting motor to the storage battery 
when it is desired to have the starting motor crank the engine. 
The switch is mounted on the floor board in front of the driver’s 
seat in such a position that it may be operated by the heel of the 
driver’s right foot. The main body of the switch is on the under¬ 
side of the floor board and it is operated by a round plunger 
which extends vertically through a hole in the floor board and 
projects a short distance above the upper surface of the board. 
The switch is closed by pushing down on the plunger with the heel. 
A view of the completed switch is shown in Fig. 362, and a cross 
section is shown in Fig. 363. The switch is held in the open posi¬ 
tion by means of a compression spring, which also serves to open 
the switch when the heel is removed from fhe plunger cap. 

The detailed construction of the switch is quite clearly shown 
in Fig. 363. The main housing is made in two parts which are 
held together by two flat headed screws. Two contact terminals 
are secured to the lower half of the housing and they form the 
main terminals of the switch. These two contact-terminals are 
connected together electrical when the switch is closed by a short 
metal bus bar mounted on the lower end of the plunger shaft. 

(g) Lamps 

Each of the two headlamps is equipped with two lamp sockets. 
The bright headlights are 6-8 volt, 17 candle power bulbs and they 
are mounted in sockets in the center of the reflectors. The dim 
headlights are 6-8 volt, 2-candle power bulbs and they are mount¬ 
ed in lamp sockets in the upper half of the reflector. The tail 
lamp is 6-8 volt, 2-candle power bulb. There is no cowl or dash 
lamp. The lamps are controlled by means of a switch mounted 
on the dash of the car within easy reach of the driver. 

(h) Combination Switch 

The current for operating the lamps and the ignition system 
is controlled by what is called a combination switch which is 
located on a small panel alongside the ammeter and the combina- 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CASR 557 


tion is mounted on the dash or cowl board of the car. The switch 
is so constructed and wired that current for the lamps is drawn 
from the battery when the engine is idle, and partly from the 
battery when the engine is operating and the generator is deliver¬ 
ing current until the value of the current delivered by the gene¬ 
rator exceed that taken by the lamps and the ignition system, if 
the ignition key is thrown to the battery position, and then the 
generator is taking care of the lamps and ignition and also charg¬ 
ing the battery. Current for opening the ignition system may 
be taken from the battery or from the magneto. A front view of 
the switch is shown in Fig. 364. 



Figs. 364 and 365 .—Front and rear view of lighting and ignition switch. 

The lights are controlled by turning the switch lever so that the 
pointer registers with the indication of the condition as desired; 
“Off, ” meaning no lights; “Dim, ” meaning dim lights; and 
“On“ meaning bright lights. The tail light burns when the lever 
is in either the “On” or “Dim” positions. 

The ignition circuit is controlled by inserting a key in the 
barrel of the level and turning the key so its position registers 
with the indication of the source of current desired. The key 
is shown in the magneto position in Fig. 364, meaning that the 
ignition current is being supplied by the magneto. 

The terminals on the back of the switch are marked to indicate 
which wires should be attached to them. A rear view of the 
switch is shown in Fig. 365. 





558 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 



Fig. 366.— F. A, Ford wiring diagram 











































































F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 559 


(i) Connecting Leads or Wiring 

A complete wiring diagram is shown in Fig. 366. A very heavy 
cable leads from the positive terminal of the battery to one ter¬ 
minal of the starting switch and is marked in the figure battery 
to switch wire. A second heavy cable leads from the remaining 
terminal of the starting switch to the insulated terminal on top 
.of the starting motor, and is marked in the figure starting switch 
to motor wire. Another heavy short cable connects the negative 
terminal of the battery to the frame of the car and is marked in 
the figure battery to frame ground wire. 



Fig. 367 .—Terminal block. 

A multiple conductor cable composed of five conductors leads 
from the terminal block on the front side of the dash to the lights, 
magneto and foot switch. A view of the terminal block is shown 
in Fig. 367. The five wires in this cable have different colored 
insulations and they make the following connections. The red 
wire is connected to the left-hand binding post on the terminal 
block and leads to the magneto terminal. The yellow wire is 
connected to the second binding post on the terminal block and 
leads to the starting switch terminal. The green wire is connected 
to the third binding post on the terminal block and leads to the 
tail lamp. The brown wire is connected to the fourth binding post 



560 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

on the terminal block and leads to the large lamp in the left-hand 
headlight. The gray wire is connected to the fifth binding post 
on the terminal block and leads to the small lamp in the left-hand 
headlight. 

The following connections are made by means of a six con¬ 
ductor cable from the instrument board to the terminal block and 
the ignition coil. The red wire is connected from the terminal on 
the back of the combination switch marked “Mag” to the left- 
hand binding post on the terminal block. The yellow wire con¬ 
nects from one terminal on the ammeter to the second binding post 
on the terminal block. The green wire is connected from the term¬ 
inal on the back of the combination switch marked “Rear” to the 
third binding post on the terminal block. The brown wire is con¬ 
nected from the terminal on the back of the combination switch 
marked “D” to the fourth binding post on the terminal blocK. 
The gray wire connects from the terminal on the back of the 
combination switch marked “L heads” to the fifth binding post 
on tne terminal block. The black wire connects from the terminal 
on the back of the combination switch marked “Coil” to the 
common terminal of the four ignition coils. 

Another six conductor cable makes the following connections. 
The black, red, blue and green wires connect from the distributor 
to the four terminals of fhe ignition coils. The brown wire con¬ 
nects from the fourth binding post on the terminal blocli to the 
large lamp in the right-hand headlamp. The gray wire connects 
from the fifth binding post on the terminal block to the small 
lamp in the right-hand headlamp. 

A single black wire leads from the terminal on the cutout to 
one of the terminals on the back of the ammeter and from this 
same terminal on the ammeter the connection is extended by a 
piece of black wire to the terminal on the back of the combina¬ 
tion switch marked “Bat.” 

A black wire connects from the first binding post on the termi¬ 
nal block to the horn switch, and another black wire connects 
from the horn switch to the horn. 

Four high-tension wires lead from the high-tension terminals of 
the coils to the spalrk plugs in the tops of the four cylinders. The 
cylinders are numbered consecutively from the front end of the 
engine toward the rear. The firing order is one, three, four, two. 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 561 


Electrical Circuits 

The principal electrical circuits of the F. A. starting and light¬ 
ing system may be easily traced by reference to the wiring dia- 
terminal of the generator you pass through the cutout contacts, 
gram shown in Fig. 366. 

Charging Circuit : Starting with the positive or undergrounded 
terminal of the generator you pass through the cutout contacts, 
when they are closed, along the black wire to one terminal of the 
ammeter, through the ammeter and along the yellow wire to the 
second binding post on the terminal block, then along another 
yellow wire to one terminal of the starting switch, then along the 
heavy battery to switch cable to the positive terminal of the bat¬ 
tery, through the battery to the negative terminal which is ground¬ 
ed to the frame of the car then along the frame of the car to the 
negative terminal of the generator which is also grounded to the 
frame of the car, through the armature winding to the positive 
terminal, thus completing the circuit. If the electrical pressuxo 
of the generator exceeds the pressure of the battery a current will 
flow through the battery from its positive terminal toward its 
negative terminal and the battery is said to be charging. The 
value of the charging current will be indicated on the ammeter. 
This charging operation will continue as long as the generator 
pressure exceeds the battery pressure and when the generator 
pressure drops below the battery pressure the circuit will be opened 
by means of the cutout and it will not be closed again until the 
generator pressure has increased to a value greater than the 
battery pressure. 

Starting Motor Circuit : Starting with the positive terminal of 
the storage battery you can trace along the heavy cable to the 
starting switch, then through the starting switch when it is closed, 
then along the starting switch to motor cable, through the field 
windings of the starting motor, through the armature of the start¬ 
ing motor to the grounded terminal or frame of the car, along the 
frame to the negative terminal of the storage battery which is 
also .grounded, through the storage battery to the positive terminal, 
thus completing the circuit. 

Lighting Circuits : Starting with the positive terminal of the 
battery you can trace along the heavy battery to switch cable, 
then through the yellow wire to the second binding post on the 


562 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


terminal block, then through another yellow wire from the second 
binding post on the terminal block to one terminal of the ammeter, 
through the ammeter to the battery terminal of the combination 
switch. Now if the lighting switch is thrown to the position mark¬ 
ed “On” the circuit will be completed as follows: from the 
terminal on the back of the combination switch marked “L head" 
along the gray wire to the fifth binding post on the connecting 
block and from this point the circuit divides, a gray wire lead¬ 
ing to each of the large bulbs in the head lamps through the 
bulbs to the frame of the car or ground, then along the frame of 
th^car to the negative terminal of the battery which is also ground¬ 
ed through the battery to the positive terminal thus completing 
the circuit. If the lighting swittch is thrown to the position mark¬ 
ed “Dim" the circuit from the combination switch will be com¬ 
pleted as follows: from the terminal marked “D" along the 
brown wire to the fourth binding post on the terminal block, and 
from this point the circuit divides a brown wire leading to eacli 
of the small bulbs in the headlamps, through the bulbs to the 
frame of thq^ car and the remainder of the circuit is the same as 
for the large lamps. With the lighting switch in either the 
“Dim" or “On" positions a circuit through the tail lamp will 
be established as follows: from the terminal on the back of the 
combination switch marked “Rear" along the green wire to the 
third binding post on the terminal block, along another green wire 
to the tail lamp, through the bulb to the frame of the car, or 
ground, back to the negative terminal of the battery, through 
the battery to the positive terminal of the battery thus complet¬ 
ing the circuit. 

Battery Ignition Circuit : Current for ignition purposes will be 
supplied by the battery when the ignition key is turned into the 
position marked “Bat" and the circuit may be traced as follows: 
The circuit from the positive terminal of the battery to the 
“Bat" connection on the back of the combination switch is the 
same as for the lights which was traced in the previous paragraph. 
From the terminal on the back of the combination switch marked 
“Coil" you can trace along the black wire direct to the coil 
terminal which is common to one side of each of the four primary 
windings. The circuit will be completed through each of the four 
primary windings in regular order by means of the timer which 
will ground one end of each of the black, red, blue and green 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 563 


wires leading from the primary windings of the coils to the 
timer. The grounding of each of these wires in turn completes 
the circuit back to the negative terminal of the battery through 
the battery to the starting point. 

to the first binding post of the terminal block, then along the black 

Horn Circuit : From the magneto terminal along the red wire 
wire to the horn switch, from the horn switch along another black 
wire to the horn terminal, through the horn winding to the frame 
of the car and back to the grounded terminal of the magneto. 

Maintenance of F. A. Electrical System 

The maintenance of the F. A. starting and lighting system may 
for convenience be divided into the following five groups. 

Maintenance of Generator 

Maintenance of Motor 

Maintenance of Cutout 

Maintenance of Storage Battery 

Maintenance of the Electric Wiring 

Each of these different groups will b« discussed in detail in the 
following paragraphs. 

Maintenance of Generator 

A general classification of the most likely generator troubles 
is given in the table entitled Generator Trouble Chart. It will be 
observed that all of the generator troubles are classified as being 
either mechanical or electrical and they will be discussed accord : 
ing to this classification. 

Generator Mechanical Troubles 

The mechanical troubles usually experienced in the operation 
fo the generator are as a rule confined to the following: 

(a) Loose Driving Gear 

(b) Broken Bearing 

(c) Armature off Center 

(d) Shaft Bent 

(e) Commutator Bursted 

Each and every one of the above mechanical troubles can be 
located by a careful visual inspection of the generator. 


514 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


(a) For example, take hold of the gear by hand (it is assumed 
the generator has been removed from the ear) and you can easily 
determine if it is firmly keyed to the shaft. 

(b) The armature may be turned by hand to see if it runs freely 
and noiselessly. If it is found that the armature sticks or turns 
hard, the bearings should be examined to see if they are broken 
thus allowing the armature to drag on the pole pieces. 

(c) If the armature turns hard or seems to drag it may be off 
center due to worn bearings, which can be easily determined by 
observing the freedom of the armature in the bearings, or the 
drag may be due to a loose pole piece, which is caused by one of 
the heavy screws holding the pole pieces in place against the in¬ 
side of the generator frame becoming loosened. The remedy for 
the trouble, if it is due to worn bearings, is to put in new bearings, 
and if it is due to a loose pole piece to tighten up the screw 
holding the pole piece in place. A punch mark should be placed 
in the outer edge of the screw after it is drawn up tight which 
will prevent its becoming loosened as easily as it might otherwise. 

(d) A bent armature shaft is a somewhat unusual occurrence but 
it will cause the armature to appear to be out of balance and may 
even cause it to drag on the pole pieces. It is practically im¬ 
possible to straighten a shaft and the best and safest remedy is 
a new armature. 

(e) A bursted commutator cannot be repaired and the only 
remedy is to put in a new one. A bursted commutator will usually 
be accompanied by considerable other damage such as broken 
brushes, brush holders, and perhaps the armature winding will 
be injured. A new armature will doubtless be the cheapest and 
safest in the end instead of trying to put on a new commutator. 

In order to inspect the brushes, which are located at the rear 
end, it will be necessary to remove the rear end cover band which 
is held to the end bracket by means of two screws. In order to 
remove the armature, the brushes must be raised from the commu¬ 
tator by pulling them up in their holders by means of the brush 
pig-tails. The brushes will be held free from the commutator by 
means of the brush springs which will press the brushes against 
the side of the holders. The screws holding the front end bracket 
should be removed now and the bracket and armature may be com¬ 
pletely removed from the frame. 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 565 

The back end bracket may be removed from the frame by 
removing the four screws holding it in position and then loosen¬ 
ing it from the frame. The short leads connected to the brushes 
will not permit the end bracket being removed but a short distance 
from the generator frame and if it is desired to remove it com¬ 
pletely the wires and leads will have to be disconnected. 

Generator Electrical Troubles 

In the outline of generator troubles, there are four-sub-heaa- 
ings to the electrical troubles as follows: 

(f) Open Circuits 

(g) Short Circuits and Grounds 

(h) Third Brush Troubles 

(i) Cutout Troubles 

(f) Open circuits are more commonly due to a dirty commutator, 
worn commutator, brushes being stuck, improper or no spring 
pressure on the brushes, brushes too short or broken, and broken 
brush connections. Some of the more uncommon causes of open 
circuits are an open field winding, open armature winding and a 
broken connection between the commutator and the armature wind¬ 
ing proper. 

One of the first tests to make on the generator is to operate it as 
a motor by connecting it direct to a six-volt storage battery with 
an ammeter in circuit. If the generator does not operate as a 
motor when it is connected to the battery and there is no reading 
on the ammeter you know immediately that there is an open circuit 
If the generator operates slowly as a motor and there Is a current, 
of less than five amperes it is an indication that there is a partial 
open circuit or a poor connection in the generator circuit which 
does not allow the proper amount of current to flow. 

The open circuit may be located by means of the test points by 
testing the different sections of the circuit through the generator 
starting from the insulated terminal on top of the frame and con¬ 
tinuing to the grounded terminal. 

A simple testing outfit for locating opens is shown in Fig. 368. 
If tb.e test points be applied to the terminals of a circuit or a por¬ 
tion of a circuit and the electrical connection between the points 
where the test points are applied is complete the circuit through 
the test lamp will be complete and the lamp will light unless the 


566 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


Generator Trouble Chart 


*3 


o GO 

o o 
© 


8 o 


Broken bearing 
Loose pinion 
Loose pole piece 
Commutator burst 
Bent shaft 


[Indicated by noise, 

| low current or no 
[ current generated 


Brush 

rigging 


£3 3 
© o . 

Q 1 -3 Armature 


o 

© 

g-£< 

u O 
W 03 


Fields 

Brush 

rigging 

Armature 

Fields 


Brush connections 
Brush stuck 
• Brush too short 
Brush spring broken 
Dirty commutator 

{ Intense blue sparking 
at commutator 
and flatted 
commutator bars 

( No current generated 
If partial open— 
low current 

{ Main terminal 
Brush connections 
Brush holders 


Indicated by 
low current gen¬ 
erator or no 
current 
at all 


( Low or no 
current 
generated 


( Excessive heating of 
armature. Insulation 
burned—low generation 

[Coils heat 
l Low current 
[ generated 


[No current 

Commutator-! generated or 
[ low current 


•E-S 

H-o 


Incorrect setting 
Brush not sanded in 
Spring pressure not right 


Indicated by charging 
current being too high 
or too low and not 
remaining constant at 
x high speed 
[No current to battery 
Open j Generator very hot— 

[ will burn out generator quickly 

Battery will discharge back 
through generator at about 
Closed 20 amperes when engine 

is not running. This will 
discharge battery. 














F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 567 

resistance of the circuit between the test points is too high. The 
test lamp will have full battery voltage applied at its terminals 
when the test points are connected directly together, while if the 
test points are connected with a resistance between them the full 
voltage of the battery will not be applied to the lamp and it may 
not burn depending upon what voltage is actually applied to its 
terminals. If the resistance of the circuit being tested and the 
resistance of the lamp are equal then the voltage of the battery 
will be divided equally between them. 

The connection between the insulated terminal and the positive 
brush can be tested by applying one of the test points to the 
terminal and the other one to the brush. If the connection is com- 



Fig. 368 .—Simple testing outfit. 


plete the test lamp will light. The electrical connection between 
the insulated brush and the commutator may be tested in a similar 
manner by applying one test point to the brush and the other one 
to the commutator. The field winding should now be disconnected 
from the third brush and test made to determine the electrical 
connection between the third brush and the commutator and also 
between the grounded brush and the commutator. The field may 
be tested by applying the test points to its terminals. If the field 
circuit is open, each coil may be tested separately and the exact 
one in which the trouble exists determined. An open circuit can 
thus be localized by means of the above tests and the necessary 
steps may be taken to remedy the trouble. 

The commutator should be examined to see that it is clean, as 
a dirty commutator will prevent good electrical contact between 
the brushes and the commutator bars. If the commutator is dirty 
due t° grease and dirt it may be easily cleaned by using a piece of 









568 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

clean rag moistened in gasoline. A fine pointed piece of hard wood 
should be used in removing the dirt and grease from between the 
commutator bars. The mica insulation between the commutator 
bars is cut away a short distance below the surface of the commu¬ 
tator, or undercut as it is commonly called, which allows the 
brushes to make better contact with the commutator if the grooves 
are kept free from all foreign substances. 

Quite often a dirty commutator is due to sparking at the brushes, 
and in such cases it will be necessary to sand it by means of a 
strip of very fine sand paper preferably not coarser than No. 00. 
The sand paper should be applied to the commutator by placing it 
over the end of a piece of wood and then holding the end of the 
piece of wood against the commutator while the commutator is re¬ 
volving. The end of the piece of wood should be cut off true so 
as to prevent grooves being cut in the surface of the commutator. 

If the surface of the commutator is badly worn so as to allow 
the mica insulation between the bars to become flush with the 
surface of the commutator thus preventing the brushes from mak¬ 
ing good electrical contact with the commutator, there is only one 
remedy and that is to undercut the mica. The commutator surface 
should first be trued up by taking a small cut off of it in a lathe 
and then the mica should be cut away from between the bars to 
a depth of about 1/32-inch. An end view of the commutator with 
the mica correctly cut away is shown in Fig. 569, and one in which 
it is incorrectly cut away is shown in Fig. 373. A convenient tool 
for cutting away the mica may be made from an old hack saw 
blade by grinding off the sides of the teeth so that the saw will 
make a cut the same width as the mica and then providing a suit¬ 
able handle for it as shown in Fig. 371. The groove in the mica 
372, and the saw then used. Be careful in using the saw not to 
may be started by means of a three-cornered file as shown in Fig. 
mar the edges of the commutator bars any more than you can help. 
The rough burs along the edges of the bars should be removed by 
means of a fine file and the commutator surface well sanded before 
it is put into service. 

An open circuit may be caused by the brushes sticking in their 
holders and if such is found to be the case the brushes and brush* 
holders should be thoroughly cleaned so that the brushes move 
freely under the action of the spiral springs pressing them on the 
surface of the commutator. 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 569 

An open circuit between the brushes and commutator may be due 
to not having sufficient spring tension on the brushes so as to hold 
them in contact with the commutator. Improper spring tension on 


SEGMENTS 



WAY 

M/CA MUST BE CUT 
AWAY CLEAN BET¬ 
WEEN SEGMENTS 


SEGMENTS 



WAY 

M/CA MUST NOT BE 
LEFT W/TH A TH/N 
EDGE NEXT TO 
SEGMENTS 


Figs. 369 and 370 .—Light ana wrong way of undercutting mica in commutator. 

the brushes will result in sparking at the brushes and a burned 
and blackened commutator will result which will tend to open the 
circuit between the commutator and the brushes. A new spring 




\ 


COMMUTATOR 


SLOTT/NG M/CA WITH 



STARTING GROOVE IN 
M/CA W/TH 15- 
CORNER. ED F/LE. 


Figs. 371 and 372 .—Slotting commutator with sawblade and starting cut with three 

cornered file. 


is the best and safest remedy for this job and the commutator 
and brushes should be thoroughly cleaned. If the spring pressure 
is too great it has the effect of rapidly wearing out the commutator 
and the brushes, but is usually considered better practice than too 













































570 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

little spring pressure. The spring pressure should be sufficient to 
snap the brush back on the commutator when it is raised by pull¬ 
ing on the pig-tail and then released. 

An open circuit may be caused by the brushes being worn to 
such an extent the springs will not cause them to make electrical 
contact with the surface of the commutator. The only remedy for 
a condition of this kind is to replace the old brushes with new 
ones. The new brushes should be sanded in as shown in Figs. 373, 
374, and 375. Figs. 373 and 374 show two methods of sanding in 
the third brush while Fig. 375 shows the correct method of sanding 




Figs. 373 and 374 .—Two methods of “sanding in” third brush. 

in the two lower or main brushes and Fig. 376 shows the in¬ 
correct method of sanding in the third brush. The arc of -con¬ 
tact between the brushes and the commutator should correspond 
to the full width of the brush. 

The pig-tail connection from the brush to the brush holder may 
be broken or the connections may be loose or broken and in such 
cases there will be an open circuit from the brush to the brush 
holder or the circuit will be of comparatively high resistance. 

An open circuit in the armature winding will cause excessive 
sparking at the commutator and several of the commutator bars 
will be blackened and perhaps burned due to the sparking. A very 




F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 571 


simple and effective test for locating open circuits in an armature 
winding is shown diagrammatically in Fig. 377. An ammeter, 
one cell of a storage battery and the test points are connected 
in series. The test points are applied to adjacent commutator 
bars all the way around the commutator and the ammeter reading 
for each combination is carefully observed. In Fig. 377 the test 
points are connected to the commutator and the armature shaft 
which is correct for the ground test. If the ammeter readings 
are all the same there are no open circuits in the armature wind¬ 
ing, but if one or more readings of the ammeter differ from the 
others to any extent there is an open circuit. The open may be 
a broken wire leading to the commutator, or the wire may have 




Figs. 375 and 376 .—Correct and incorrect method of “sanding in” main brushes. 

come unsoldered from the commutator and a careful inspection 
of the armature will enable you to determine if either of these 
conditions is the cause of the trouble. If the trouble proves to 
be within the armature winding, the complete winding will no 
doubt have to be removed, and it will no doubt be cheaper to 
put in a new armature than to attempt to rewind the old one, 
unless it is an extreme emergency. 

(g) Assuming all of the mechanical difficulties have been cor¬ 
rected and that the generator will not run as a motor when it is 
connected to the storage battery but a reading of four or five 
amperes is indicated on the ammeter connected in circuit, or if 
the venerator runs very slowly as a motor and draws more current 
than it should, it is an indication that the current is not actually 







572 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


passing through the armature and field windings in the proper 
way but a portion or all of it is being shunted through a short or 
grounded connection and is thus not effective in the operation 
of the generator as a motor. The more common causes of this 
kind of trouble are grounded brushes and grounded main gene¬ 
rator terminal, and some of the more uncommon causes are 
grounded commutator, grounded armature winding, grounded field 
coils and short circuited armature or field coils. 

The insulation between the main generator terminal and the 
frame of the generator may be tested by first disconnecting the 
lead from this terminal to the positive brush from the positive 
brush holder and then apply one of the test points to the terminal 
and one to the frame of the generator. If there is no indication 




Fig. 378 .—Testing field for grounds. 


on the ammeter the terminal is insulated from the frame. If the 
ammeter shows a reading the terminal insulation is in trouble 
and a careful inspection should be made of the insulating washers 
and the insulation on the lead from the terminal to the positive 
brush. The ground may be due to dirt having collected around the 
terminal and a thorough cleaning will correct the trouble. 

The brush holders for the positive and third brushes may be 
tested for grounds by placing one of the test points on the frame 
and the other point on the holder, the field connection to the third 
brush having been removed, and a piece of paper placed between 
each of the brushes and the commutator. If a ground shows up 
the trouble is due to dirt or poor insulation and an inspection 
will determine the exact cause of the trouble. The negative 









F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 573 

brush holder is grounded permanently and the test does not 
apply to it. 

Both terminals of the field should be disconnected from the 
brushes as shown in Fig. 378 and then one test point applied to 
the field and one to the frame of the generator. If the test shows 
a ground then disconnect the windings from each other and test 
each of them separately. The field coil found to be in trouble 
should be removed and the necessary repairs made or a new one 
substituted. A test should be made after the coil has been put 
back in place first on the individual coil and then on the entire 
field after the coils are reconnected. The commutator under 
normal conditions is insulated from the shaft of the armature 
and there is no electrical connection between it and the shaft. 
The commutator may be tested for grounds when it is in the 
generator by first removing the brushes from the commutator or 
by placing pieces of paper under them and then applying one of 
the test points to the commutator and the ether to the armature 
shaft as shown in Fig. 377. If there is no reading on the ammeter 
it shows that the commutator as well as the armature winding is 
insulated from the armature shaft and core. If the test shows a 
ground it may be between the armature winding and the core or 
between the commutator and the shaft. If the ground cannot 
bo ioeated by a careful inspection, it will be best to replace the 
defective armature with a new one. A grounded coil may be 
located by applying one of the test points to each of the com¬ 
mutator segments in regular order and the other test point in 
contact with the armature shaft, and each of the ammeter read¬ 
ings will be approximately the same for all of the commutator 
bars. If one of the individual commutator bars or a particular 
coil is grounded one of the ammeter readings will be larger than 
the others and this reading will occur when the test point is in 
contact with the grounded segment or the segment connected to 
the grounded coil. As stated above, a careful inspection will often 
locate the trouble. 

Short circuited coils may be located in exactly the same 
manner as that employed m locating open armature coils. If all 
the ammeter readings are approximately the same the coils are 
all in good condition, but if one or more of the readings is higher 
than the average, it is an indication that the coil connected be¬ 
tween the two segments on which the test points are placed is 


574 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

short circuited. The increase in current is due to a decrease in 
resistance caused by one or more of the turns in the coil being 
cut out of service on account of defective insulation. The exact 
location of the trouble may be determined by a careful examina¬ 
tion of the armature winding. 

A short circuit in the field winding may bp determined by 



Fig. 379 .—Testing field for short circuit:. 


sending a current through the four coils in series by means of a 
storage battery as shown diagrammatically in Fig. 379. The 
resistance of the field winding of the F. A. generator varies from 
2.7 to 3.3 ohms depending upon whether the coils are wound with 
single cotton enameled wire or double cotton covered wire. A six- 
volt storage battery should produce a current of approximately 2.5 
amperes. If the ammeter reading is noticeably larger than this it 























F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 575 


is an indication that some of the turns in one or more of the field 
coils arc shorted and it is then necessary to determine which ones 
are defective. The insulation should be removed from the joint be¬ 
tween the coils and a test made on each separate coil. The 
ammeter reading for each separate coil should be the same if they 
are all in good condition. If any one of the coils show a decided¬ 
ly higher reading than the others it indicates that a portion of 
that coil is shorted and not effective in producing a magnetic field. 
The damaged coil should be removed and repaired or replaced by 
a new one and the complete winding retested after the coils are 
all back in place and reconnected. 

(h) The operation and adjustment of the third brush has been 
described in the section on the generator and it is only neces¬ 
sary to mention the fact that the generator output is increaseu 
by moving the third brush in the direction of rotation and de¬ 
creased by moving the third brush in the opposite direction to 
the direction of rotation of the armature. The contact of the 
third brush should be as good as possible and the spring pressure 
sufficient to keep it in firm contact with the commutator. 

(i) Cutout troubles are in the majority of cases caused by 
failure to close and second by failure to open. Failure to close 
may be due to the voltage or pressure coil being open or short 
circuited and the contacts may be so dirty that they do not make 
electrical contact after they are drawn together. 

The contact may fail to open due to the points being welded 
together due to continued opening and closing of the cutout which 
causes excessive sparking. The spring tension on the armature 
may not be correct which will cause the cutout to open and close 
at the wrong time. 

The electrical circuits of the cutout may be tested by means of 
the test points and the contact may be cleaned with a very fine 
emery cloth or with a very fine jewelers file. The internal cir¬ 
cuits of the dash and generator types of cutouts are shown in 
Figs. 353 and 354. 


576 


ELECTRICAL EQUIPMENT OF THE MOTOR CAR 


Maintenance of Motor 

Motor troubles are classified the same as generator troubles 
and a complete chart of these troubles is given for the conven¬ 
ience of the reader. 

Motor Mechanical Troubles 

The principal mechanical troubles are as follows: 

(a) Broken or Worn Bearing 

(b) Armature off Center 

(c) Shaft Bent. 

(d) Commutator Bursted 

(a) The bearings on the motor are solid instead of ball bear¬ 
ings as in the case of the generator. The motor runs a very small 
percentage of the time that the generator is run and for this 
reason the solid bearings will meet all of the requirements if 
they are protected by not allowing any dirt to get into them when 
they are taken out. If upon inspection the bearings are found 
to be badly worn they should be replaced with new ones. Worn 
bearings or a badly bent shaft may allow the armature to drag on 
the pole pieces and cause some serious damage. 

(b) The armature may drag and appear to be off center due to 
one or more of the pole pieces being loose and the remedy for a 
condition of this kind is to draw the pole piece back in place by 
tightening the screw which holds it. It is advisable to place a 
rather deep punch mark in the outer edge of the screw after it 
is drawn up which will keep it from working loose so easily. 

(c) A bent armature shaft is more likely to occur in the opera¬ 
tion of the motor than in the case of the generator and especially 
if the spark lever is advanced to such an extent that the engine 
**kicks back”. It is almost impossible to straighten a bent shaft 
and the quickest and best way is to put in a new armature. 

(d) A bursted commutator usually causes considerable other 
damage especially to the brushes and brush holders. The best 
practice is to replace the old armature with a new one as the 
cost and inconvenience in making the repairs will amount to 
more than a new armature. 


Motor troubles 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 577 

Motor Trouble Chart 


J 2 


fH 

O O 


Worn bearings 
Shaft bent 
Commutator burst 
Loose pole piece 
Broken bendix 
Armature off 
center 


{ Pigtails 
Brushes 
not 

contacting 


All indicated by 
excessive current draw 
and slow cranking or 
complete failure to crank 
and excessive noise 


S'3 

0-3 


Brushes too 
short, poor 
spring pres- 
sure—dirty 
or burned 
commutator 


All indicated by 
low current or no 
current and failure 
to crank. If only 
partial open occurs 
the current draw 
will be low and 
cranking slow 


{Intense blue spark 
Arma- j at brush and flatted 
ture | commutator with 
[ slow cranking 


Fields 


fNo current 
\No cranking 


73 

c' 

3 
o ■ 

J K o 


Fields [Excess current 
\Slow cranking 


{ Excess current 
Burnt insulation 
Slow cranking 




Commu- fExcessive current 
tator \No cranking 


[Main terminal 
Brush I Brush holders 
rigging | Pigtails and 
[ connectors 


[Indicated by excessive 
j current and no 
j cranking, or 
[ slow cranking 













57 3 ELECTRICAL EQUIPMENT OF THE MOTOR CAR 

Motor Electrical Troubles 

In the outline of motor troubles there are two sub-headings as 
follows 

(e) Open circuits 

(f) Short circuits and grounds 

(e) Open circuits are more commonly due to dirty commutator, 
worn commutator, brushes stuck in the holders, improper or no 
spring pressure, brushes too short or broken, broken brush con¬ 
nections, open field circuit, open armature circuit and a broken 
connection between the commutator and armature windings. An 
open circuit in the starting motor may be detected by making a 
free running test on it with an ammeter in circuit. If the motor 
fails to run and there is no reading on the ammeter it indicates 
that the motor circuit is open. If the motor runs very slowly and 
takes considerably less than 75 amperes it indicates that there 
is a partial open circuit or a poor connection or contact some 
place in the motor circuit. The general method of locating open 
circuits in the case of the motor, except for the armature, i> 
practically the same as in the case of the generator which has 
already been described in detail. The resistance of the winding 
of the motor armature is so very low that the method employed 
in the case of the generator cannot be used satisfactorily for the 
motor armature. The only place that an open circuit is likely to 
occur is where the ends of the coils connect to the commutator 
bars and it can usually be detected by a careful inspection. The 
wires should be raised from the slot in the commutator riser and 
thoroughly cleaned, then resolder in place. An open armature 
coil causes a “flat” to develop due to continuous arcing at that 
particular spot. The internal connections of the motor are shown 
diagrammatically in Fig. 357. 

(f) If the motor fails to turn or turns very slowly when you are 
making the free running test and it draw T s a current quite a bit 
larger than 75 amperes it is an indication that there is a ground 
or short circuit in the motor. Troubles of this kind are likely 
to occur due to grounded brush holders, grounded main motor 
terminal, grounded armature winding, grounded field windings, 
short circuited armature coils, and short circuited field coils. 

The tests for grounds in the case of the motor are practically 


F. A. STARTING AND LIGHTING SYSTEM FOR FORD CARS 573 


the same as in the ease of the generator, but the shorts can not 
be easily located as in the case of the generator, on account of 
the very low resistance of the armature windings. The only 
practical method of locating shorts in armature coils is by means 
of a 11 growler” unless the trouble is indicated visually by burned 
or flatted commutator bars. 

Maintenance of Storage Battery 

The storage battery is really the heart of the electrical system 
and for this very reason it should not be neglected. The prin¬ 
cipal points to bear in mind in taking care of the storage bat¬ 
tery are the following: 

(a) Keep the plates covered with electrolyte by adding water 
or acid as conditions may require. 

(b) The battery should ke kept in a charged condition and 
under no circumstances allowed to stand for any length of time 
in a discharged condition. 

(c) The terminals to the battery should be cleaned occasionally 
so as to prevent undue corrosion. 

(d) The battery should be firmly anchored in position so as to 
prevent its being bounced about. 

Maintenance of the Electric Wiring 

In maintaining the electric wiring in connection with the F. A. 
starting and lighting system the following suggestions should be 
observed. 

(a) See that all connections are clean, tight and making good 
electrical contact. 

(b) See that all wires are properly anchored in place and not 
subject to mechanical abrasion. 

(c) Keep all wires as free from dirt and oil as possible. 

(d) Inspect the ground connections occasionally to see that 
they are tight and making good electrical contact. 




































































































-t 








































* 







INDEX 


A 


Active materials, Lead 

storage cell . 96 

Adjustment of regulator 

output. 221 

Adlake-Newbold combined 
regulator and cutout, 

Wiring diagram . 214 

Airplane spark plugs. 445 

Alarms, Buzzer . 455 

, Mechanically operated 
, Two principles of elec¬ 
trical . .. ....... 455 

Allis-Chalmers combined 
regulator and cutout, 

Wiring diagram of. 206 

Alternating current gener¬ 
ator, Simple . 155 

Ammeter and voltmeter, 
Measuring car power by 71 

, Weston combined. 356 

Ammeter measures both 
currents, Magnetic vane 350 
, Most common type of 351 
, Plunger type for both 

currents .. 349 

shunt in parallel with 
coil, Connection for.. 354 

shunts . 355 

, Simple, for measuring 

direct current . 348 

, Weston portable . 352 

Ammeters and voltmeters, 

Combined .. 357 

Ammeter and voltmeter 
handy for tracing elec¬ 
trical troubles . 507 

Ampere-hour capacity of 

battery . 91 

capacity of dry cell. 91 

581 


capacity of storage cell 107 

meter . 357 

meter, Generator output 

regulated by . 220 

meter, Regulation of 

generator output by.. 191 

Analysis of trouble . 495 

Angle of lag in motor.. 247 

Armature and field cur¬ 
rents, Magnetizing ef¬ 
fects of . 197 

, Multiple-coil . 231 

, Multipolar ring. 165 

reaction in motor .. 243 

reaction, Methods of re¬ 
ducing .. 252 

, Ring . 234 

, Simple drum . 165 

speed of generator and 
speed it generates, 

Relation between . 178 

winding, Electrical pres¬ 
sure induced in . 166 

winding on a Delco gen¬ 
erator . 199 

winding on Delco gen¬ 
erator, Diagram of. 198 

Arrangement of F.A., 
brushes and brush 

holders . 551 

Artificial magnets .. 117 

Atwater-Kent closed-cir¬ 
cuit battery ignition 

system .. 406 

open-circuit interrupter 403 

timer-distributor . . 406 

Automatic electromag¬ 
netic pinion shift. 279 

Auburn car, Wiring dia¬ 
gram of Delco instal¬ 
lation on . 620 





































582 


INDEX 


B 


Back-kick releases. 287 

Batteries and lamps in 
series, Methods of con¬ 
necting . 39 

, Distinction between 
primary and secondary 95 
in series, Decrease of 

pressure in . 41 

, Two, do not always 
operate satisfactorily.. 57 
Battery, Ampere-hour ca¬ 
pacity of . 91 

, Best results obtained 

in charging . 112 

charging, Calculating re-, 

sistance for . 42 

, Direction of currents 

when, charging . 184 

, Filling and testing 

electrolyte.105 

generator ignition . 398 

ignition system, Bosch.. 409 
ignition system, Remy 

closed-circuit . 415 

ignition system, Connec¬ 
ticut . 411 

ignition system, Dia¬ 
gram illustrating 

principle of. 398 

ignition system on mag¬ 
neto base. 407 

ignition system, Pitts¬ 
field . 414 

ignition system, 

Rhoades . 418 

ignition system, West- 
ignition system, timing 451 

inghouse .... 417 

, Result when pressure 
of generator drops be¬ 
low pressure of . 186 

or generator, Pressure 
by not all available at 

terminals . 40 

Battery and generator, 
Connecting and dis¬ 
connecting . 486 


ignition circuit, F.A. 562 

Bell, Electrically-operated 457 
Bell-shaped magnet for 

Mea magneto . 382 

Belt drive for generator.. 300 
driven generator on 
eight-cylinder engine 297 
Bendix drive or automatic 


pinion shift . 280 

Bendix drive, factors of 
safety in various parts 

of. 555 

of F.A. starter. 554 

Berkshire magneto . 379 

Bijur engine and motor 
connection system ap¬ 
plied on Packard . 291 

Bipolar machine with one 
field coil, Magnetic 

field of . 168 

magnetic circuit with 

two field coils . 168 

magnetic field with one 

coil ..,. 169 

Bosch battery ignition 

system . 409 

combined distributor 

and breaker . 409 

flywheel starter on the 

Marmon . 292 

motor and engine con¬ 
nection system, Elec¬ 
trical circuit of . 284 

voltage regulator . 210 

Bosch-Rushmore electro¬ 
magnetic drive, Old. 283 

Brakes, Electric .. 464 

Breaker and distributor 
of Remy battery igni¬ 
tion system . 417 

and distributor system, 

Connecticut . 409 

mechanism, Remy . 417 

mechanism, Westing- 


Brushes and loop seg¬ 
ments, Arrangement of 159 
on a direct current mo- 










































INDEX 


tor, Proper position 

of. 

Brush system, Diagram of 

Delco . 

Brushes and brush 
holders, Arrangement 

of F. A. 

Bucking coil, Regulation 

produced by .. 

series field winding. 

Buzzer test set . 

Buzzer alarms . 

electric horns . 

C 

Cable connections, F. A.... 
Carbon-disc resistance, 
Operation of U.S.L. 

regulator with . 

Carbon field resistance, 
Electromagnet used in 

combination with . 

, Use of in constructing 

field resistances . 

Care to be exercised in re¬ 
turning electrolyte to 

cell . 

Care of generators and 

starting motors . 

of storage battery . 

Cars, Series water cir¬ 
cuit employed on early 
Causes of, Dirty com¬ 
mutator . 

Cell, capacity, Decrease 

in . 

capacity varies, due to 
temperature changes.. 

, Causes of local action 

in ... 

, Chemical jction in . 

condition ca/mot be de¬ 
termined by measur¬ 
ing pressure . 

current, Effect of temp¬ 
erature on . 

, Electrical pressure in 

a clry —. 


583 


, Methods employed to 

depolarize .. 85 

dls and plates, Arrange¬ 
ment of in storage bat¬ 
tery .... 103 

, Production of number 
of connected in par¬ 
allel .. 93 

, Proper combination 
for best results . 93 


, Specific gravity of 


should be determined 
at regular intervals.. Ill 
Centrifugal governor, 
Generator operated by 
slipping clutch con¬ 
trolled by . 218 

Chain drive for charging 

generator . 301 

on Colonial eight, In¬ 
closed . 298 


driven dynamometer .... 299 
Charging circuit, F. A. 

of North East system. .. 5G1 
Charging battery, Best 

results obtained in. 112 

battery, Direction of 

currents when. 184 

battery, Method of 

placing lamps in 

series when . 76 

generator, Chain-drive 

for . 301 

position of starting 

switch . 319 

storage batteries, De¬ 
termining cost of . 76 

storage cell, Chemical 

action in when. 100 

Chemical action in cell. 84 

action in a storage cell 
during charge and 

discharge . 99 

action in storage cell 

when charging . 100 

action in storage cell 

when discharging . 98 

Circuit for the cowl light 490 
for tail-light . 490 


245 

327 

548 

194 

193 

510 

.455 

458 

560 

210 

209 

209 

106 

501 

505 

28 

568 

108 

108 

86 

84 

42 

91 

90 










































584 


INDEX 


Circuit, Tracing the . 

Circuit-breaker, Fuses 

and . 

Circuit ignition systems, 
Current consumption 

for . 

, Multipolar magnetic 

four-pole . 

Circuits, Complete elec¬ 
trical made of many 

parts . 

, Difference between 
electrical and ordin¬ 
ary . 

, Electrical . 

, High and low-pressure 
in the motor car, Major 

, Open and closed . 

, Parallel or multiple. .. 
, Resistance of parallel 
, Wire resistance in 

parallel . 

Classification of lamps by 

base ... 

of wiring systems. 

Classification of troubles, 

simple tests . 

Cleaning commutator . 

Cleaning old reflectors. 

Closed-circuit battery 
ignition system, At¬ 
water-Kent . 

cell .. 

Closed-circuit battery 

windings . 

Clutch first used in con¬ 
necting starting motor 

to engine . 

Coercive force explained.. 
Colonial eight inclosed 

chain drive .. 

Combination switch and 

dimmers, Ford . 

Commutation . 

Commutator and brushes 
Low generator output 
due to improper care of 
, Four-segment . 


, Operation of two-part 227 

Commutator, cleaning. 567 

slatting, with sawblade 
and starting cut with 

three-cornered file. 569 

Compass needle, Effect of 
current through wire 

loop on . 132 

Complete circuits, Test¬ 
ing out . 518 

Component parts of the 
starting, lighting and 
ignition system, Func¬ 
tion of . 485 

Compound generator . 175 

motors . 258 

motors, Field windings 

of ..,. 240 

Condenser in jump spark 

coil, Purpose of . 370 

Conductance of the elec¬ 
trical circuit . 47 

Conductor, Production of 
force acting on ex¬ 
plained .. 223 

Conductors and insulators 

defined . 23 

, Factors determining 

resistance of . 23 

, Resistance of . 25 


Conductor’s movement, 
Left-hand rule to de¬ 
termine direction of.. 225 
Connecticut battery igni¬ 
tion system . 411 

breaker and distributor 

system . 409 

Methods of . 500 

Connection of shunt field 
on third-brush machine 199 
Connections for charging 
storage batteries .. .113, 114 
for various positions of 


controller . 481 

of a series generator.... 173 
Conservation of energy.... 66 
Constant current and.con¬ 
stant voltage output. 180 


Constant voltage and con- 


489 

330 

402 

170 

11 

10 

10 

65 

12 

399 

43 

45 

46 

335 

313 

512 

567 

337 

406 

86 

232 

268 

122 

298 

533 

248 

221 

160 











































INDEX 


stant current generator 

systems . 

Contact points, Gage for 

adjusting . 

Containers for lead 

storage cells . 

Controller and single elec¬ 
tromagnet, Connecting.. 
, Various position of.... 
Conventional Wiring sym¬ 
bols . 

Coulomb, Definition . 

C o u n t e r-electromotive 

force . 

Cowl light, Circuit for.... 

Crank-operated horns. 

Cross-magnetizing and 
demagnetizing ampere- 

turns . 

Cumulative action of 
series and shunt field 

windings . 

compound generator. 

Current, Action of bat¬ 
tery in electrical. 

and speed. Torque and 

armature .. 

consumption for circuit 

ignition systems . 

, Difficulty of determin¬ 
ing which of two or 
more wires at a junc¬ 
tion are taking the. 

, Effect of resistance 

of electrical . 

induced in coil by mov¬ 
ing a magnet . 

induced in a wire by a 

magnet . 

lag ...-. v - 

, Production of in in¬ 
duction coil . 

relations, Example il¬ 
lustrating . 

relations for the par¬ 
allel circuit . 

relations in a series 

circuit . 

through wire loop, Ef- 


585 


feet of on compass 

needle . 132 

Currents induced in a 

wire by a magnet. 141 

, Oscillographs for re¬ 
cording variations in 402 
, Plunger ammeter type 

for both . 349 

, Pressure and resis¬ 
tance, Relation of. 21 

Cutout, Arrangement of 

windings on . 188 

, Generator output and 

purpose of . 177 

, Purpose of . 181 

, Simple magnetic. 182 

, Two-pole . 187 

Cutouts, Terminals of- 
two-pole . 188 


D 

Decrease in cell capacity.. 108 
dynamotor, Motor and 
generator winding on 264 
dynamotor, Operation 


of . 263 

generator, Armature 

winding on a . 199 

generator, Diagram of 
armature winding on 198 

ignition relay . 428 

ignition relay and inter¬ 
nal connections . 431 

junior ignition system, 

Wiring diagram of.433 

open-circuit ignition 

system . 424 

open-circuit interrupter 425 
resistance unit function 425 
Demagnetizing and cross- 
magnetizing ampere- 

turns . 247 

Demagnetization of mag¬ 
net, Cause of . 121 

Depolarization explained.. 85 
Depolarizing cell, Methods 
employed . 85 


191 

425 

102 

205 

480 

487 

16 

253 

490 

457 

247 

192 

176 

15 

256 

402 

489 

' 20 

144 

141 

400 

150 

33 

49 

32 











































586 


INDEX 


Determining direction of 

magnetic field . 

Device for automatically 
advancing and retard¬ 
ing spark . 

Diagram illustrating pos¬ 
sibilities of starting 

motor.location . 

illustrating principle of 
battery ignition sys¬ 
tem . 

of Delco brush system., 
of high-tension magneto 
circuits, Simplified.... 

, Wiring, see Wiring 
diagram 

Differential action of ser¬ 
ies and shunt field 

windings . 

Difficulty of determining 
which of two or more 
wires at a junction are 

taking the current. 

Dimming headlights, Sim¬ 
ple device for . 

Direct current generator, 

Simple . 

generator with two 
loops of wire and 
four segments in 

commutator . 

motor and right-hand 

rule, Principle of. 

motor, Proper position 

of brushes on . 

motors, Excitation of.... 

motors, Principle of. 

, Simple ammeter for 

measuring . 

Direction indicators, Sig¬ 
nals and . 

of induced current de¬ 
pends upon direction 

of motion . 

of induced pressure. 

of magnetic field. 

of pressure, Determin¬ 
ing . 

Dirty commutator, Causes 
of . 


Distributor and breaker, 


Bosch combined . 409 

Dixie magneto . 378 

Double-deck arrangement 
of motor and generator 

in Saxon four. 291 

Dry cell . 89 

, Ampere-hour capacity 

of . 91 

Internal resistance of.... 90 

Dry cells, Testing . 90 

Drum armature, Simple.... 165 
switch, Wagner-Electric 

Co.’s rotating or. 324 

Dual and double-ignition 

systems . 437 

Dual power car, Wiring 

diagram of Woods . 476 

type of interrupter. 430 

Dynamo as generator and 

motor . 154 

Dynamometer, Splitdorf- 

Apelco chain-driven. 299 

Dynamotor . 261 

as starting and lighting 

unit ... 262 

, Operation of Delco .... 263 


E 

Eisemann two-part im¬ 
pulse starter . 390 

Electric alarms, Two 

principles of . 455 

and water circuits com¬ 
pared, Parallel . 43 

battery, What consti¬ 
tutes . 92 

brakes . 464 

Electric braking . 484 

circuit, Parallel.44, 45 

gearshift, Principle of 

operation . 466 

gearshift, Wiring of.... 471 
gearshifts and trans¬ 
missions . 466 

heaters . 461 


131 

396 

289 

398 

327 

388 

192 

489 

341 

158 

159 

226 

245 

238 

223 

348 

462 

146 

146 

129 

149 

568 













































INDEX 


Electric horns, Care of. 

lamps . 

light bulbs,. Forms of 

filaments of . 

lighting circuit, Series 

motors . 

signals and accessories 

vulcanizers .:. 

Electrical and mechanical 
power, Relation be¬ 
tween ... 

and ordinary circuits, 

Difference between. 

and water circuits. 

and water circuits com¬ 
pared ..... 

and water circuits con¬ 
trasted .-.----- 

and water circuits, 
Measuring difference 

in pressure ........ 

and water circuits, 

Operation of . 

and water circuit, 

Simple . 

Circuit, Conductance 

of . 

circuit, Damage due to 

electrolysis . 

circuit for low-candle- 

power headlights . 

circuit, Nature’s great 
water circuit typical 

of the . 

circuit of Bosch system 
circuit of the cut-out, 

Testing . 

circuit, Voltmeter meas¬ 
ures differ in pres¬ 
sure between termin¬ 
als of . 

circuits . 

circuits, F.A. 

circuits and fundamen¬ 
tals . ; . 

circuits. Boosting pres¬ 
sure in . 

circuits, Complete, made 
of many parts. 


587 


circuits, Maintenance 

and repair of . 498 

circuits, Testing . 505 

circuits, Pressure es¬ 
sential factor in. 20 

current, Action of bat¬ 
tery in . 15 

current, Effect of re¬ 
sistance of . 20 

energy, Measurement of 75 
force measured in volts 58 
instrument operating 
on heating effect of 

current .. 353 

instruments . 345 

power . 70 

power, Measurement of 72 
pressure in a dry cell 90 
pressure induced in 

armature winding. 166 

pressure in parallel. 55 

pressure in secondary 

winding, Value of. 386 

pressure of magneto on 
armature core, Varia¬ 
tions in . 376 

pressure, Variation in 

156, 158, 160 
troubles, Ammeter and 
voltmeter handy for 

tracing . 507 

, Generator . 565 

, How to diagnose. 498 

, motor . 578 

wiring, Maintenance of 579 
Electrically-operated bell 457 
Electricity, Action of 
under definite condi¬ 
tions . 10 

and the motor car. 9 

, its unknown value. 9 

moving force . 17 

, Path in which it flows 10 
, Resistance to flow, of 19 
Electrochemical equiva¬ 
lent explained . 87 

Electrodes, Arrangement.. 442 
, Gap between spark 
plug . 450 


458 

333 

333. 

29 

223 

454 

465 

73 

10 

20 

64 

10 

18 

14 

14 

47 

87 

490 

13 

284 

575 

30 

10 

561 

9 

35 

11 
















































588 


INDEX 


Electrolysis, Damage to 
electrical circuit due to 
Electrolyte, Determining 

specific gravity of. 

, Filling battery and 

testing . 

for lead storage bat¬ 
teries . s 

in cell, Changes in 

specific gravity of. 

, Preparation of . 

, Returning to cell, 
Care to be taken in.... 
Electromagnet, Connec¬ 
ting controller and 

single .. 

for controlling field 

circuit connections .... 
for opening field cir¬ 
cuit of generator. 

used in combination 
with carbon field 

resistance . 

drive, Old Bosch-Rush- 

more . 

induction . 

regulation of a genera¬ 
tor . 

regulation of generator 

output . 

regulator, Operation of 

Electromagnetism . 

Energizing bucking coil 
by magnetic vibrator.... 
Energy, Conservation of.. 

explained . 

in a motor car, Trans¬ 
formation of . 

not electricity, stored 

in storage cell . 

Engine and motor connec¬ 
tions . 

shaft, Generator and 

motor mounted on. 

speed date . 

for different cars, rela¬ 
tion between . 

Entz magnetic trans¬ 
mission . 


transmission, Merits of 484 
Equipment, Starting, 
lighting and ignition.... 305 
Examples illustrating 

current relations . 33 

illustrating relations of 
parallel circuits . 51 

F 

F. A. battery ignition 

circuit . 562 

cable connections . 560 

charging circuit . 561 

combination switch . 556 

cutout . 545 

electric motor . 549 

circuits . 561 

system, maintenance of 563 
, Ford wiring diagram.. 558 

generator . 538 

starting and lighting 
system for Ford cars 538 

storage battery . 545 

Factors determining re¬ 
sistance of conductors .. 2 ^ 

of safety in various 
parts of, Bendix drive 555 
Fastening magnetos in 

position, Methods of. 388 

Faure plate . 97 

Field circuit connections. 
Electromagnet for con- 

# trolling . 217 

circuit of generator. 
Electromagnet for 

opening . 212 

, Magnetic, Permanent 
magnet provides simple 
method of producing .. 168 
resistance, Solenoid and 

“mprriiro well if nnn 


trol of . 316 

Resistance, Varying the 
value of by solenoid. .. 213 
resistance, Use of car¬ 
bon in constructing .. 209 
windings for generators • 
and motors . 168 


87 

105 

99 

103 

107 

105 

106 

205 

217 

212 

209 

283 

141 

200 

191 

201 

129 

209 

66 

69 

68 

95 

266 

302 

544 

543 

477 








































INDEX 


589 


windings of compound 

motors . 240 

windings of series mo¬ 
tors . 239 

windings of shunt mo¬ 
tors . 238 

Filaments of electric light 

bulbs, Forms of . 333 

Flux, Magnetic, on a gen¬ 
erator and its generated 
pressure, Kelation be¬ 
tween . 178 

Flywheel starter, Bosch, 

on the Marmon . 292 

Focusing headlights . 340 

Force acting on con¬ 
ductor, Production of 

explained . 223 

Force, Counter-electromo¬ 
tive . 253 

defined . 58 

, Electricity moving. 17 

Ford car, F.A. starting 
and lighting system for 538 
Single-ignition system 

on . 436 

Wiring diagram of 
single ignition system 

on . 436 

combination switch and 

dimmers . 533 

electrical system, Stock 524 

headlights, Lighting 

circuit for . 532 

horn circuit . 532 

, Ignition system on. 530 

oil troubles . 535 

, Overcoming ignition 

trouble on . 533 

steering post, Special 
dimmer and leads to 

special switch on. . 531 

Four-coil ring armature 
with four-segment com¬ 
mutator . 162 

Four-cylinder high-ten¬ 
sion ignition system. 366 

low-tension ignition sys¬ 
tem . 364 


Four high-tension igni¬ 
tion systems on one 

engine . 437 

Four-segment commutator 160 
Frame and end brackets 
of F.A. starting motor, 

Dimensions of . 550 

Friction clutch . 273 

clutch for operating 

generator . 219 

drive, Gray and Davis.. 296 
drive magneto . 387 


Function and description 
of each component part 
of F.A. electrical system 538 
of the component parts 
of the starting, light¬ 
ing and ignition sys¬ 


tem . 485 

of the starting switch.... 556 
Fundamental principles 

of storage battery. 95 

Fundamentals and elec¬ 
trical circuits . 9 

Fuses and circuit-breaker 330 

G 

Gage for adjusting con¬ 
tact points . 425 

Gear and chain-drive 

magneto . 388 

and motor drives, Com¬ 
bined . 303 

drive for charging gen¬ 
erator .. 302 

driven generator on 
Amalgamated engine 300 
housing, Inclosed, 

North-East system. 304 

reduction, Westing- 
house starting motor 306 

reductions . 304 

Gearshift, Electric, 
Principle of operation.. 466 
Gearshifts and transmis¬ 
sions, Electric . 466 

Generator and battery 
Connecting and discon¬ 
necting . 486 









































590 


INDEX 


Generator and motor ac¬ 
tions, Combining . 

and motor, Dynamo as 
and motor, interchange¬ 
able . 

engine shaft .. 

and storage battery, 
Simple connection of— 
Armature speed of, 
and speed it gener¬ 
ates, Relation be¬ 
tween . 

, Belt drive for . 

cylinder . 

changed to motor, Di¬ 
rection in which it 

will operate . 

cutouts, Location of. 

cutouts, Position of 
switch when engine 

is idle . 

, Direct current, with 
two loops of wire and 
four segments in com¬ 
mutator . 

Generator drive, purpose 

of . 

, electrical equipment 

of . 554, 

Generator electrical 

troubles ..1. 

Electromagnetic regu¬ 
lation of .... 

Friction clutch for op¬ 
erating . 

Friction drive for. 

Gear drive for charging 
, Gear-driven, on Amal¬ 
gamated engine . 

, Maintenance of . 

mechanical troubles. 

clutch controlled by 
centrifugal governor.. 
Generator output; and 

purpose of cutout. 

, Electromagnetic regu¬ 
lation of . 

Inherent regulation of.. 
, Low, due to improper 


care of commutator 

and brushes . 221 

, Mechanical regula- 


regulated by ampere- 

hour meter ._. 200 

, Regulation of .j. 191 

, Regulation of by 

ampere-hour meter. 191 

, Regulating . 504 

, Manual . 189 

Generator: 

, Principle of . 155 

, Simple alternating 

current . 155 

, Simple djrect current 158 

, Speed of depends 
upon speed of device 

driving it . 177 

systems, Constant-volt¬ 
age and constant cur¬ 
rent . 191 

Generators and motors...... 154 

and motors, Field wind¬ 
ings for . 168 

Generators and starting 
motors, Care of. 501 


friction grounded sys¬ 
tem, Wiring diagram 320 
grounded wire system.. 320 
Ground in lamp circuit by 
testing lamp, Testing 


for . 514 

Ground return wire, 
Remy, applied to Oak¬ 
land . 314 

Grounds, for testing arm¬ 
ature . 572 

, Testing field for . 572 

H 

Hand-operated horns. 457 

Haynes cars, Wiring 

diagram of. 

Headlights, Simple device 

for dimming . 341 

Heaters, Electric . 461 

Heating device, Manifold 462 


311 

154 

225 

302 

181 

178 

300 

297 

241 

189 

190 

159 

290 

557 

565 

200 

219 

296 

302 

300 

563 

563 

218 

177 

191 

191 













































INDEX 


High and low-pressure 

circuits . 

High-tension ignition sys¬ 
tem . 

magneto . 

and automatic timing 
device, Eisemann’s.... 
magneto circuits, Sim¬ 
plified diagram of. 

magnetos, Safety gap 

for . 

Horn circuit, Ford. 

Horns, Buzzer electric. 

care of electric. 

, Crank operated . 

, Hand-operated . 

Horseshoe magnets, Mag¬ 
netic fields produced by 
How to diagnose elec¬ 
trical troubles. 

Hydrogen gas, Accumula¬ 
tion of in the positive 

plate . 

Hysteresis . 

I 

Ignition circuit, control of 

lights and control .. 

device transforms elec¬ 
trical energy into 

heat energy . 

, Component parts of 
starting, lighting and 

system on a Ford. 

Ignition trouble on Ford 
Impulse starter, Eise- 

mann two-piece. 

Induced current, Direc¬ 
tion of depends upon 

direction of motion . 

current, Right hand 
rule for finding di¬ 
rection of . 

magnetism . ; . 

pressure, Direction of. 

pressure, Value of. 

Induction coil applied to 
ignition of motor car 
engine .- 


591 


coil, Production of cur¬ 
rent in . 150 

Induction, Electro-* 

magnetic . 141 

Ignition circuit time 

constant . 400 

Early methods . 360 

relay and internal con¬ 
nections, Delco. 431 

relay, Delco . 428 

wiring and timing. 451 

Ignition system: 

, Four-cylinder high- 

tension . 366 

, Four-cylinder low- 

tension . 364 

, High tension . 362 

, Jump-spark . 363 

, Low-tension . 361 

, Philbrin . 422 

, Single . 434 

, Wiring diagram of 

Delco . 432 

Ignition systems. 360 

, Dual and double. 437 

, Four high-tension on 

one engine . 437 

Inherent regulation of 

generator output . 191 

Installing spark plugs, 

Various methods of. 449 

Instrument operating on 
heating effect of cur¬ 
rent Electrical . 353 

Instruments, Electrical.... 345 
Insulated terminal and 
positive brush, testing 

connection between . 567 

Insulators and conduc¬ 
tors defined . 23 

Internal connections, Del¬ 
co ignition relay and.... 431 

resistances . 39 

Interrupter, Atwater- 

Kent open-circuit < . 403 

, Delco open-circuit. 425 

Dual type of... 430 

with resistance unit. 429 


65 

362 

383 

396 

388 

384 

532 

458 

458 

457 

457 

235 

498 

85 

140 

557 

486 

485 

530 

533 

390 

146 

148 

119 

.146 

145 

151 





















































592 


index: 


J 

Jaw clutch, Overrunning 
Joints in wiring, Solder¬ 
ing . ; . 

Jump-spark coil, Con¬ 
struction of . 

Jump coil, Purpose of 

condenser in . 

ignition system . 

K 

Kinetic energy defined. 

K.W. Ignition Co.’s mag¬ 
neto . 

L 

Lamp filaments . 

reflectors .„. 

reflectors, Care of. 

Lamps, Equipment of. 

Lamps and batteries In 
series, Methods of con¬ 
necting . 

, Classification by base 
, Connecting in series.... 

, Trouble . 

Lead cells, General types 

of .,. 

storage batteries, Elec¬ 
trolyte for . 

storage cell active ma¬ 
terials . 

storage cells . 

storage cells, Arrange¬ 
ment of plates in. 

storage cells, Con¬ 
tainers for . 

Lead storage cells plate.. 

Leakage, Magnetic . 

Leclanche cell . 

Leese-Neville Co.’s rotat¬ 
ing or drum switch. 

Left hand, or motor, 
rule to determine direc¬ 
tion of conductor’s 

movement . 

Light and wiring switches 


Lighting circuit for Ford 


headlights . 532 

Lights and ignition on 

circuit, Control of. 557 

Lights, head, tail and side 334 
Lines of force in mag¬ 
netic field . 126 

List of testing apparatus 512 
Local action in the cell, 

Causes of . 86 

Importance of wiring 

diagram, in . 497 

Location and control of 

switches . 328 

of generator cutouts. 189 

of starting motors. 287 

Locations of different 
parts of a starting, 
lighting and ignition 

system illustrated . 492 

Long shunt compound 

machine . 176 

Loop segments and 
brushes, Arrangement 

of . 159 

Low-candle power head¬ 
lights, Electrical cir¬ 
cuit for . 490 

Low-tension ignition sys¬ 
tem . 361 

magneto . 381 

magneto, using high- 

tension distributor. 383 

Low-voltage testing lamp, 
Arrangement of . 508 

M 

Magnet, Cause oi de¬ 
magnetization of . 121 

, Current induced in 

coil by moving a. 144 

for Mea magneto, Bell¬ 
shaped . 382 

, Permanent, provides 
simple method of pro¬ 
ducing magnetic field 168 
, Poles of a . 117 


267 

498 

369 

370 

363 

67 

377 

333 

337 

338 

556 

39 

335 

343 

461 

97 

103 

96 

96 

101 

102 

96 

238 

88 

323 

225 

340 












































INDEX 


593 


Magnetic attraction and 

repulsion . 

Magnetic braking . 

circuit, Construction of 

motor . 

circuit of bipolar ma¬ 
chine with one field 

coil . 

circuit, Ohm’s law for 

the ... 

circuit, Reluctance of.... 
circuit with two field 

coils, Bipolar . 

circuits, Parts of. 

cutout, Simple . 

field, Determining di¬ 
rection of . 

field, Direction and 

strength of . 

field, Direction of. 

Magnetic field with one 

coil Bipolar. 

field, Lines of force in 
fields produced b y 
horse-shoe magnets.... 

fields, Types of.169, 

flux . 

flux on a generator 
and its generated 
pressure, Relation be¬ 
tween . 

leakage . ------ 

material, Ability of to 
retain its magnetism 
material, Steel best and 

most expensive. 

needle .. 

Magnetic pole of unit 

strength .. 

screen . 

spark plug . 

vane ammeter measures 

both currents . 

vibrator and lead con¬ 
trol, Inserting resis¬ 
tance in field circuit 

intermittently by. 

vibrator, Energizing 
bucking coil by. 


vibrator, Inserting re¬ 
sistance in field, cir¬ 
cuits intermittently 

by . 200 

Magnetism Molecular 

theory of . 123 

Magnetizing effects of 
armature and field cur¬ 
rents . 197 

Magneto base, Battery ig¬ 
nition on . 407 

, Friction drive . 387 

, Fundamental prin¬ 
ciple of . 372 

, Gear and chain-drive.. 388 

, High-tension . 383 

K.W. Ignition Co.’s. 377 

, Methods of fastening 

in position . 388 

, Simple form of. 375 

Magneto terminal con¬ 
nections . 528 

, Testing . 511 

Magnetomotive force. 135 

forces in series and 

parallel . 138 

Magnetos, Mounting and 

driving by gears. 388 

Magnets and magnetism.. 117 

, Artificial . 117 

, Forms of . 119 

, Saturated or mag¬ 
netized . 122 

Maintenance and repair 
of electrical equipment 498 

, Points on . 498 

of electrical wiring. 579 

of F.A. electrical sys¬ 
tem . 563 

of generator . 563 

of motor . 576 

of storage battery. 579 

Major circuits in the 

motor car . 12 

Make-and-break ignition.. 153 
spark coil, Principle'of 367 
Manifold heating device.. 462 


Manual generator cutouts 189 
generator cutouts, Posi- 


118 

477 

237 

168 

137 

13b 

168 

172 

182 

131 

125 

129 

169 

126 

235 

235 

177 

178 

238 

122 

237 

128 

124 

128 

444 

350 

207 

209 



















































594 


INDEX 


tion of switch when 

engine is idle. 190 

Master switch and neu¬ 
tralizing device . 468 

Mea magneto . 380 

Measurement of electrical 

energy . 75 

of electrical power. 72 

Measuring motor power 

by wattmeter . 73 

Mechanical and electrical 
power, Relation between 73 
regulation of generator 

output .191, 218 

troubles, Generator. 563 

, Motor . 576 

Mechanically-o p e r a t e d 

alarms . 456 

“Mercury well” and sole¬ 
noid control of field re¬ 
sistance . 216 

Meter, Ampere-hour. 357 

, Watthour . 359 

Method of placing lamps 
in series when charging 

battery . 76 

Methods of connecting to 
terminal posts, ground, 

etc. 500 

Mica in commutator, 
right and wrong way 

of undercutting . 569 

Molecular theory of mag¬ 
netism . 123 

Motor and engine connec¬ 
tions .... 266 

and engine connection 
system, Bijur, ap¬ 
plied on Packard. 291 

and gear drives, Com¬ 
bined . 303 

Motor and generator ac¬ 
tions, Combining. 311 

and generator in Saxon 
four, Double deck ar¬ 
rangement of . 291 

and generator,. Inter¬ 
changeable . 225 


and generator windings 


on Delco dynamotor.. 264 

, Angle of lag in. 247 

, Armature reaction in 243 
car, Electricity and the 9 
car engine, Induction 
coil applied to igni¬ 
tion of . 151 

car propelled by com¬ 
bined gasoline and 
electric power plants 472 
car. Transformation of 

energy in a . 68 

, General requirements 

for starting . 266 

, Generator changed to 
Direction in which it 

will operate . 241 

Motor electrical troubles.. 578 

, Maintenance of . 576 

mechanical troubles. 576 

trouble chart . 577 

magnetic circuit, Con¬ 
struction of . 237 

Motor torque, Measuring.. 78 
, Torque produced by.... 254 

Motors and generators. 154 

, Excitation of direct 

current . 238 

Principle of direct Cur¬ 
rent .:. 223 

Mounting and driving 
magnetos and by gears 388 

Multiple-coil armature. 231 

Multiple-voltage systems.. 317 

wiring system . 316 

Multipolar magnetic four- 

pole circuit . 170 

Multipolar ring armature 165 
Multipole switches, Single 
and .1. 323 

N 

Nature’s great water cir¬ 
cuit typical of the elec¬ 
trical circuit . 13 

Neutralizing device and 
master switch . 468 











































INDEX 


595 


Nomenclature of impor¬ 
tant parts of Splitdorf 
low-tension magneto .... 
Non-automatic pinion 

shaft . 

Non-magnetic materials 
North and south poles of 
solenoid, Easy method 

of finding . 

North-East system in¬ 
closed gear housing. 

0 

Oersted, the unit for 
measuring reluctance.... 
Ohm’s law for the mag¬ 
netic circuit . 

Oil troubles, Ford ... 

Operation of electrical 

and water circuits . 

Operating voltage of 
single and multiple sys¬ 
tems ....... 

open and closed circuits 
Open-circuit ignition sys¬ 
tem, Delco ... 

windings . 

Oscillographs for record¬ 
ing variations in cur¬ 
rents .. 

Output of a generator in 

watts . 

of motor ...... 

Overrunning jaw clutch.. 
ratchet-and-paul clutch 

roller clutch . 

P 

Parabolic reflectors . 

Parallel and series cir¬ 
cuits compared . 

circuit, Current rela¬ 
tions for . 

circuit, Pressure rela¬ 
tions of . 

circuits, Determining 

resistance of . 

circuits, Examples il¬ 
lustrating relations 

of . 


Parallel electric and 
water circuits compared 43 

electric circuit .44, 45 

or multiple circuits. 43 

water circuit. 44, 45 

Path in which electricity 

flows . 10 

Philbrin ignition system.. 422 
Pinion shift,” Automatic 

electromagnetic . 279 

, Bendix drive or auto¬ 
matic . 280 

, Non-automatic . 274 

Piston travel and spark 
advance, Determining 

relation between . 396 

Pittsfield battery ignition 

system . 414 

Plante plate . 97 

Polarity indicator . 88 

Polarity of solenoid. 134 

Polarization of the posi¬ 
tive plate . 85 

Poles of a magnet. 117 

Position of switch when 

engine is idle . 190 

Potential energy defined.. 67 
Pressure and resistance 

currents, Relation of. 21 

by battery or generator 
not all available at 

terminals . 40 

, Determining direction 
of . 149 

essential factor in 

electrical circuits. 20 

in batteries in series, 

Decrease of . 41 

in electrical circuits, 

Boosting . 35 

in series . 34 

in unequal resistances 
in series, Variation in 31 
in water circuit, Boost¬ 
ing . 34 

, Measuring difference 
in electrical and 
water circuit .. 18 


385 

274 

121 

135 

304 

136 

137 

535 

14 

317 

399 

424 

231 

402 

180 

254 

267 

272 

269 

340 

52 

49 

49 

48 

51 













































596 


INDEX 


Pressure of generator 
drops below pressure 
of battery, What hap¬ 
pens when . 

relations for series cir¬ 
cuit . 

relations of the parallel 

circuit . 

, Value of induced. 

Pressures in parallel. 

produced by two bat¬ 
teries opposed t o 

each other . 

Primary and secondary 
batteries, Distinction 

between . 

and secondary cells. 

and secondary coils. 

batteries . 

cell, Action of. 

Priming spark plugs. 

Production of number of 
cells connected in par¬ 
allel . 

Protective devices, 
Switches and. 


Relation between engine 
speed for different cars 543 
Relation between starting, 


186 lighting and ignition 

functions . 305 

29 Reluctance in series and 

parallel . 138 

49 of magnetic circuit. 136 

145 Remy battery ignition 
53 system, Breaker and 

distributor of . 417 

breaker mechanism. 417 

'56 closed-circuit battery 

ignition system. 415 

ignition system, with 
95 two igniting sparks, 

83 Wiring diagram of.... 439 

149 ground return wire ap- 

82 plied to Oakland. 314 


83 Repair and maintenance 
445 0 f electrical equipment 498 

Resistance for battery 
gg charging, Calculating 42 

in field circuit intermit- 
oiq tently by magnetic vi¬ 
brator, Inserting. 200 


R 

Ratchet-and-paul clutch, 


Overrunning . 272 

Reading wiring diagrams 485 

Reducing armature re¬ 
action, methods . 252 

Reflectors, Care of lamp.. 338 

, Cleaning old . 337 

, Parabolic . 340 

Regulating generator out¬ 
put . 504 

Regulation of generator 

output . 191 

produced by bucking 

coil . 194 

Regulator equipment, Ad¬ 
justment of . 221 

, Operation of electro¬ 
magnetic . 201 


in field current inter¬ 
mittently by magnetic 
vibrator and lead 

control, Inserting. 207 

of series circuit. 28 

of dry cell Internal. 90 

of parallel circuits. 45 

to flow of electricity.... 19 

unit function, Delco. 425 

unit, Interrupter with.. 429 
Resistances, Unequal, in 
series, Variation of 

pressure in.. 31 

Rhodes battery ignition 

system . 418 

Right-hand rule for find¬ 
ing direction of induced 

current . 148 

, Principle of direct 

current motor and. 226 

Right and wrong way of 










































INDEX 


597 


undercutting mica in 

commutator . 

Ring armature . t . 

armature, Four-coil, 
with four-segment 

commutator . 

armature, Simple . 

Roller clutch, Overrun¬ 
ning . 

Rotating or drum switch, 
Leese Neville Co. 

S 

S. A. E. standards for 

spark plug shells. 

Safety gap for high- 

tension magnetos . 

“Sanding in,” third brush, 

two methods of. 

Saturated, or magnetized, 

magnets ........... 

Secondary and primary 

coils . 

cells, Primary and . 

winding, Value of elec¬ 
trical pressure in. 

Self-excited shunt gen¬ 
erator, Operation of...... 

Series and parallel cir¬ 
cuits compared. 

and parallel, Magneto¬ 
motive forces in..... 

and shunt field wind¬ 
ings, Cumulative ac¬ 
tion of . 

circuit . 

circuit, Arrangement of 

parts . 

circuit, Current rela¬ 
tions in a . 

circuit, Pressure rela¬ 
tions for . 

circuit, Resistance of.... 
electric lighting circuit 
electrical and series 
water circuits com¬ 
pared . 

field winding . 


Series field, generator. 173 

generator, Connections 

of . 173 

motor, Operation of. 257 

motors, Field windings 

of . 239 

spark plug . 442 

water and series elec¬ 
trical circuits com¬ 
pared . 27 

water circuit employed 

on early cars. 28 

Shift pinion and switch 
contractor, Westing- 

house . 275 

Short circuited coils, Lo¬ 
cating . 573 

Short in lamp circuit by 
testing lamp, Testing 

for . 514 

Shunt field on third- 
brush machine, Connec¬ 
tion of . 199 

generator . 174 

generator, Operation of 

self-excited . 179 

motor, Operation of. 255 

motors, Field windings 

of . 238 

Signals and accessories, 

Electric . 454 

and direction indicators 462 
Simms-Huff multiple-volt¬ 
age wiring system. 316 

Simms magneto . 379 

Simple testing outfit. 567 

Single and multiple 
switches . 323 


and multiple systems, 
Operating voltage of 317 
ignition and single unit 
systems are not sim¬ 
ilar . 436 

ignition system . 434 

ignition system on Ford 

cars . 436 

unit starting, lighting 
and ignition system .. 312 

voltage systems . 317 

Slipping clutch controlled 


569 

234 

162 

161 

269 

323 

447 

384 

570 

122 

149 

83 

386 

179 

52 

138 

192 

27 

38 

32 

29 

28 

29 

27 

172 

















































598 


INDEX 


by centrifugal gover¬ 
nor, Generator opera¬ 
ted by . 

Slotting commutator, with 
sawblade and starting 
cut with three-cornered 

file . 

Soldering joints in wiring 
Solenoid and “mercury 
well” control of field 

resistance . 

, Easy method of find¬ 
ing north and south 

poles of . 

, or coil with a number 

of turns. 

, Polarity of . 

Spark advance and piston 
travel, Determining re¬ 
lation between .’. 

coil, Principle of make- 

and-break . 

, Eisemann’s device 
for Automatically ad¬ 
vancing and retarding 
plug electrodes, Gap be¬ 
tween . 

Spark plug shells, S. A. 

E. standards for. 

plugs . 

plugs, Airplane . 

plugs, Priming . 

plugs, Straight-thread¬ 
ed .. 

plugs, Various methods 

of installing . 

plugs, Waterproof . 

timing . 

Special dimmer and leads 
to special switch on 

Ford steering post. 

Specific gravity of cells 
should be determined at 

regular intervals. 

Specific gravity of elec¬ 
trolyte in cell. Changes 

in . 

of electrolyte, Deter¬ 
mining . 


of storage battery ma¬ 
terials, Changes in.... 104 

Speed of motor . 254 

Splitdorf-Apelco chain 

driven dynometer . 299 

Splitdorf low-t e n s i o n 
magneto, Nomenclature 

of important parts . 385 

Spotlights and mountings 459 
Standard equipment on a 
Ford, Wiring diagram 

of . 529 

Starting and lighting, 
electrical equipment for 

Ford cars, F. A. 538 

Starting and lighting 

unit, Dynamotor as . 262 

Starting, lighting and 
ignition system, Com¬ 
ponent parts of . 485 

, Locations of different 

parts, illustrated . 492 

Starting, lighting and 

ignition equipment . 305 

, lighting and ignition 
equipment, Three 
fundamental parts for 307 
, lighting and ignition 
functions, Relation be¬ 
tween . 305 

Starting motor, Direct 

application of . 386 

motor, Gear reduction 

on Westinghouse . 306 

Starting motor, General 

requirements . 266 

motor location, Diagram 
illustrating possibili¬ 
ties of . 289 

motor, Westinghouse, 

on Chalmers six . 292 

motors . 359 

motors, Location of . 287 

position of starting 


switch, Charging posi¬ 
tion of . 319 

Steel best and most expen¬ 
sive magnetic material.. 237 


218 

569 

498 

216 

135 

132 

134 

396 

367 

396 

456 

447 

441 

445 

445 

446 

449 

444 

394 

531 

111 

107 

105 










































INDEX 


599 


Stock Ford electrical 

system ... 

Storage batteries: 

, Care of ... 

, Connections for 

charging .113, 

, Determining cost of 

charging . 

Storage battery: 

and generator, Simple 

connection of . 

, Arrangement of cells 

and plates in . 

, Care of when not in 

service .. 

, Fundamental princi¬ 
ples of . 

, Maintenance of . 

materials, Changes in 

specific gravity of. 

Storage cell: 

, Ampere-hour capacity 

of . 

, Chemical action in 
during charge and 

discharge . -- 

, Chemical action in 

when discharging . 

stores energy, not 

electricity .. 

, Watthour capacity of.. 
Storage cells, Arrange¬ 
ment of plates in lead- 

plate, Lead . 

, Types of . 

Straight-threaded spark 

plugs . 

Sumpter impulse starter.. 
Switch, Position of when 

engine is idle ...... 

Switches and protective 

devices .-. 

, Control and location . 

, Various types of . 

T 

Taillight circuit . 

Telephone test set. 


Temperature changes 

varies cell capacity . 108 

, Effect of on cell 

current . 91 

Terminal connections. 

Magneto . 528 

Terminals of two-pole 

cutouts . 188 

Test set, Buzzer . 510 

Testing apparatus, List of 512 
armature for grounds .. 572 
connection between in¬ 
sulated terminal and 

positive brush . 567 

dry cells . 90 

electrical circuits of the 

cutout . 575 

electrical equipment . 505 

field for grounds . 572 

Testing for a ground in 
lamp circuit by testing 

lamp . 514 

for short in lamp cir¬ 
cuit by testing lamp 514 
lamp, Arrangement of 

low-voltage . 508 

magneto . 511- 

out complete circuits .... 518 

outfit, Simple . 567 

Third-brush machine. 195 

Three-unit starting, light¬ 
ing and ignition system 308 
Three-unit, single-w i r e 
electrical system, Wir¬ 
ing diagram of. 494 

Time constant, Ignition 

circuit . 404 

Timer-distributor, A t- 

water-Kent . 406 

Timing battery system. 451. 

device, Eisemann’s 
high-tension magneto 

and automatic . 396 

Torque and armature cur¬ 
rent and speed. 256 

produced by motor.. .... 254 
required to run engine 
at definite speed, De¬ 
termining . 81 


524 

110 

114 

76 

181 

103 

115 

85 

579 

104 

107 

99 

98 

95 

107 

101 

96 

96 

446 

391 

190 

319 

328 

325 

490 

511 















































600 


INDEX 


Torque starting motor Voltage coil . 82 

must develop, Determin- Voltage output, Constant 

ing ..... 80 current and constant.... 180 

Tracing the Circuit. 489 regulator, Bosch. 210 

Transmission, Entz mag- Voltmeter measures dif- 
netic .. 477 ference in pressure be- 


, Merits of Entz. 484 

parts, Arrangement of.. 479 

Trouble, Analysis of. 495 

chart, Generator. 566 

, Motor . 577 

Trouble lamps . 461 

Troubles and causes, 
classification of, simple 

tests .. 510 

Two methods of “sanding 

in” third brush. 570 

T w o-p art commutator,- 

Operation of .. 227 

Two-pole cutout . 187 

Two-spark ignition. 440 

Two-types of F.A. auto¬ 
matic cutouts. 547 

Two-unit starting, light¬ 
ing and ignition system 309 
Types of magnetic fields.. 235 

Typical installation . 486 

wiring system . 520 


U 

Undercutting mica in 
commutator, right and 


wrong way of. 569 

Unit of inductance. 153 


Using a wiring diagram 493 
U.S.L. regulator and out¬ 
put, Wiring diagram of 211 
regulator with carbon- 
disc resistance, Oper¬ 
ation of . 210 

V 

Variation in electrical 

pressure . 156, 158, 160 

Various, steps in making 

wire joint . 499 

Varying the valve of field 
resistance by solenoid.... 213 


tween electrical circuit 


terminals . 30 

, Principles of . 355 

Voltmeter and ammeter 
handy for tracing elec¬ 
trical troubles . 507 

Voltmeters, Combined am¬ 
meters and . 357 

Volts, Electrical force 

measured in . 58 

Vulcanizers, Electric.. 465 


W 

Wagner-Electric Co. ro¬ 
tating or drum switch 324 
Water and electrical cir¬ 
cuit, Simple . 14 

Water and electrical cir¬ 
cuits .20, 64 

and electrical circuits 

contrasted . 10 

circuit, Boosting pres¬ 
sure in . 34 

circuit. Parallel .44, 45 

pressures in parallel. 54 

Waterproof spark plugs.. 444 

Watts, Output of a gen¬ 
erator in . 180 

Watthour capacity of 

storage cell .". 107 

meter . 355 

meters, Two forms of.... 75 

Wattmeter a combined 
ammeter and voltmeter 355 
, Measuring motor 

power by. v . 73 

Westinghouse battery ig¬ 
nition system... 419 

breaker mechanism. 420 

head, tail and side 

lights . 334 

shift pinion and switch 
contractor . 275 













































INDEX 


601 


Westinghouse starting 
motor on Chalmers six.. 
Weston combined am¬ 
meter and voltmeter. 

portable ammeter . 

Winding, Bucking series 

field . 

, Series field . 

Windings, Closed-circuit.. 

, Differential action of 
series and shunt field 
on cutout, Arrangement 

of . 

, Open-circuit . 

Wire joint, Various steps 

in making ... 

Wire resistance in par¬ 
allel circuits. 

Wiring and light switches 

and timing, Ignition. 

Wiring diagrams: 

Adlake-Newbold c o m- 
bined regulator and 

cutout .~. 

Allis-Chalmers c o in¬ 
toned regulator and 

cutout . 

Delco ignition system.... 
Delco Junior ignition 

system .. 

Gray and Davis ground¬ 
ed system . 

F.A. Ford... 


, Importance of, in 

locating trouble. 497 

with two igniting 

sparks . 439 

single ignition system 

on Ford cars. 436 

of standard equipment 


on a Ford . 529 

of three-unit single¬ 

wire electrical system 494 
of typical three-unit, 
single-wire electrical 

system . 494 

, Using . 493 

of U.S.L. regulator 

and output . 211 

of Woods dual power 

car . 476 

, Why it is of no value 

to working men. 493 

and symbols . 486 

, Reading . 485 

Wiring of electric gear¬ 
shift . 471 

of Studebaker series. 528 

symbols, Conventional.. 487 
system, Simms-Huff 

multiple-voltage . 316 

systems, General classi¬ 
fication of . 313 

, Typical . 520 

Woods dual power car. 472 

Work, Definition. 58 


292 

356 

352 

193 

172 

232 

192 

188 

231 

499 

46 

340 

451 

214 

206 

432 

433 

320 

558 






















































































































































































































































































































































































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